Chapter A1 – Particles & the structure of matter

Science 10 – Unit AChapter A1 – Particles & the structure of

matter

A1.1Safety in the laboratory

Understanding the rulesIt’s not enough to remember the rules for

conducting a lab experiment safely – you need to understand WHY those rules exist

Like any lesson in science, you’ll remember it better if youUnderstand the importance of the concept, orExperience the concept first-hand

Since I’d rather you not learn the importance of safety glasses by blinding yourself, focus on the WHY of the following rules.

Rule #1 – Wear the proper safety equipment


QUESTION:What safety equipment is mandatory for every

lab, and what is optional?


ANSWER:Safety glasses are mandatory, however, prescription

glasses are an acceptable replacement** Safety glasses must be worn on the face, not as a hair

accessory, even if you find them uncomfortable. **** We strongly discourage you from wearing contact lenses

into the lab, even if you are wearing safety glasses **Lab coats are mandatory any time chemicals are being

used (e.g. you don’t need them for a bio lab on microscopes)

Closed-toe footwear is required – no sandals or flip flopsGloves are only needed during dissections, where you are

likely to be handling a biohazardous specimen

Rule #2 – Don’t eat or drink in the lab


QUESTIONS:Suppose you know your three solutions are salt

water, sugar water and vinegar, and that none of these substances will hurt you. Why should you still not taste them?

Why is it not even a good idea to bring in a water bottle or chewing gum?


ANSWERS:We cannot guarantee that the solutions are pure, that the

glassware is clean, or that there are no chips in the beaker

You shouldn’t stake your life on being 100% right about any experiment

You could reach for your water and get something elseYou don’t want anything else on your lab bench other

than the required materialsEven water can be a dangerous chemical if mixed with

the right substanceGum can absorb fumes and increase your chance of

ingesting something

Rule #3 – Leftover chemicalsQUESTION:

What should be done with any used or unused chemical once they have been taken from the original container (the source container)?

Rule #3 – Leftover ChemicalsANSWER:

ALWAYS put any chemicals you’ve taken from the stock beaker in the waste beaker OR If it is safe to do so; with the tap running to dilute it, you can pour it down the drain.

WHY:The chemicals could have been contaminated by

something already in your beaker so it can never go back to the original container

The new chemical you made will have different properties

Some solutions, such as those containing heavy metals, will pollute local water supplies, or corrode the pipes

Rule #4 – Wash your hands thoroughly

QUESTION:When should you wash your hands in the lab?

POSSIBLE ANSWERS:A) Before starting the experimentB) After handling each chemicalC) At the end of the lab activityD) Before you eat your lunch

Rule #4 – Wash your hands thoroughly

CORRECT ANSWER:C) At the end of the lab activity

unless you spill anything on your hands while you’re working, there’s no need to wash your hands in between each chemical

you should wash your hands at the end, even if they appear clean, because some chemicals are invisible and others just plain stink.

Rule #5 – Clean up any spilled substances immediately

QUESTION:Why should you check with your teacher first before

you clean something up?POSSIBLE ANSWERS:

A) Because you should collect the spilled liquid and try to reuse it

B) Because your teacher wants as many reasons as possible to yell at you

C) Because there may be specific instructions for cleaning up that particular solution

D) Because your teacher spends less money on her clothes than you, so she doesn’t mind the risk

Rule #5 – Clean up any spilled substances immediately

CORRECT ANSWER:C) Because there may be specific instructions for

cleaning up that particular solution (Although your teacher does probably spends less money on

her clothes than you)For instance,

if you spill an acid, we will first neutralize it with a basic solution (baking soda solution)

if you spill a base, we will first neutralize it with an acidic solution (vinegar solution)

some compounds should be diluted first before wiping them up

some compounds stain your skin, and you don’t want to be known as the “splotchy kid”

Rule #6 – Pour chemicals properly

QUESTION:Which photo demonstrates the safe way of

pouring chemicals?


ANSWER:Actually none of them!

(Photo #1 is the safest)If you spill something,

immediate stop pouring and check for a break in your glassware

Precise measurements are made at eye level, not above or below your line of sight


ANSWER:Don’t get your lab partner to hold on

to your glassware while you pourEspecially with test tubes and

graduated cylinders (which are narrow), never pour chemicals into containers held in your hands – place the container on the counter or use a test tube rack

Rule #7 – Always listen to the teacher’s instructionsQUESTION:

You should know what you’re doing in the lab BEFORE you go in, so what are some reasons why you should listen to the teacher’s instructions during the lab?

Rule #7 – Always listen to the teacher’s instructions

ANSWERS:There may have been a change to the

procedure due to a lack of suppliesThere could be some kind of emergencyBecause your teacher charges a “stupid

question tax” of 5 marks if you ask her something that is in the lab procedure or was said out loud while you weren’t listening

Rule #8 – Label any containers you put chemicals in

QUESTION:One of these solutions is sugar water, one is an

acid strong enough to dissolve concrete, and one will make you go blind if you drink it. Which is which?

Rule #8 – Label any containers you put chemicals in

ANSWER:Actually, they’re all water, but

hydrochloric acid, methanol, and sugar water are all clear, colourless solutions indistinguishable by sight.

SO?Even if you think you can “keep track”

of which substance is which, label your containers to minimize your risk, and your error

Rule #9 – What to do with broken glassware

QUESTION: What’s the proper procedure if you break

glassware?ANSWER:

1) Inform your teacher2) Make sure any other students in the area

are alerted3) Your teacher will collect the large pieces,

and we will sweep up the smaller pieces4) If necessary, we will neutralize any spilled

liquid5) Broken glass goes in a special bin – do not

simply throw it out into the garbage.

Rule #10 – Safely detect the odor of a substanceQUESTION: How should you go about safely

detecting the odor of a substance? ANSWER:

You hold the container safely away from your face and use your hand to “waft” the scent towards your nose.

WHY:The smell may be too strong / irritating to get a

nose-fullYou should never put your face directly over a

container in case of splattering or fumes

Rule #11 – Tie hair back and roll up loose sleeves


QUESTION:What are three reasons why it could be

dangerous to have long hair or loose sleeves unsecured?


ANSWER:Both hair or clothing could catch on fireLoose sleeves can knock over glassware,

resulting in broken glass or spilling harmful chemicals

Both hair and clothing can absorb chemicals and further exacerbate a chemical burn/ irritation

Rule #12 – Mixing acids and water

QUESTION:What’s the proper way of mixing an acid and

water?POSSIBLE ANSWERS:

A) Pour the acid into the water – it’s less likely for acid to splash out of the container

B) Pour the water into the acid – you’re less likely to get acid on your hands this way

C) It doesn’t matter what order you mix two chemicals in, the result will be the same.


CORRECT ANSWER:A) Pour the acid into the water – it’s less likely

for acid to splash out of the containerYou always pour any acids into water rather

than vice versa because it's much more likely that the liquid being poured into will splash out of the beaker. If it's just water, then it’s not a problem; but if acid gets on your clothes or hands you can get burned badly.


CORRECT ANSWER:There’s one other good reason

why acid goes in water, and not vice versa -

If you add water to acid, the first drops of water will react exothermically with the acid, and bubble all over like it’s boiling (very dangerous!)

If you add the acid to the water, the acid reacts/ mixes completely with the water and dissipates.

So: “Do like you oughta, add acid to wat-ah”

Rule #13 – Using distilled water instead of tap water

QUESTION:What are three reasons why you get more

accurate results if you use distilled water instead of tap water?

ANSWER:Tap water will have salts dissolved in it that

can skew your resultsTap water is not necessarily neutral – in fact at

O’Leary it has a pH of about 8.5Tap water comes out at unpredictable rates,

distilled water is easier to control the flow

Practice problems:

1. List five steps that should be taken BEFORE entering the lab to perform an experiment?

2. List precautions you can take to prevent:

1. poisoning2. scalding3. eye damage

Practice problems:3. The purpose of a lab is to determine what

several “mystery solutions are”. You pick up a fresh test tube, and you pour some “mystery solution” into it and add some solute. You give it a good shake by holding your thumb over the opening and shake it up and down. You put the test tube down into the rack and look down into it to make your observations about the reaction that took place. List as many things as you can that were performed unsafely in the lab. Suggest what should have been done instead that would improve the procedure.

Practice problems:4. There are six pieces of emergency

equipment in the lab. What are they, where are they, and when/how should they be used?

5. What should be done in the following two scenarios?

While your lab partner is boiling some water, the fire alarm goes off.

Your lab partner has just poured some acid into what you thought was a beaker of water. It starts to bubble rapidly.

Practice problems (Solutions):1. List five steps that should be taken BEFORE entering the lab

or starting to perform an experiment? read the lab COMPLETELY and prepare any pre-lab

requirements prepare a pre-lab – predictions, hypotheses, and observations tables

should be prepared in advance come dressed in the appropriate clothing bring only the necessary items to the lab (text book, pre-lab,

pen/pencil) NO purses, binders, jackets, or iPods put on protective wear: goggles, lab coat, gloves (if necessary) collect solutions/ materials from the front and bring them to

your station LABEL all beakers/ materials…keep your station

organized! double check with your partners that you ALL understand the

procedure – once the lab begins you will lose marks for procedural questions

Practice problems (Solutions):2. List precautions you can take to prevent:

1. poisoning always wash your hands after the lab, don’t touch your face/ mouth during the lab never use your mouth to open containers etc.

2. scalding never touch test tubes/ beakers that are sitting in water

in case they are hot use “oven mitts” or tongs to handle any hot glassware

3. eye damage keep your safety glasses on at all times do not wear contact lenses in chemistry labs (some fumes

can cause them to melt to your eyes)

Practice problems (Solutions):3. The purpose of a lab is to determine what several

“mystery solutions are”. You pick up a fresh test tube, and you pour some “mystery solution” into it and add some solute. You give it a good shake by holding your thumb over the opening and shake it up and down. You put the test tube down into the rack and look down into it to make your observations about the reaction that

took place. You shouldn’t mix chemicals unless you have a

reasonable idea how they will reactYou shouldn’t shake glassware verticallyYou shouldn’t use thumb as a stopperNever look directly into a test tube from above

(splatters/ fumes can get in your face).

Practice problems (Solutions):Emergency equipment

Where it’s located When & how to use

Emergency shower

In the corner by the door

•Use it if you spill a large amount of chemical on your clothes•Pull the handle, strip down clothes and rinse for 15 minutes

Eye wash station Over the sink in the second lab bench

•Use if you splash chemicals in your eyes•Place your eyes directly over the two faucets, pull the metal paddle towards you, rinse for 15 minutes



Fire extinguisher In the prep room between the Chem & Bio labs

•Use if the lab is on fire!•P – pull the pin•A – aim at the fire•S – squeeze the trigger•S – sweep over the flames

Fire blanket In the corner by the green cupboards

•Use if you are on fire – “stop, drop and roll” isn’t enough•Wrap yourself in the blanket as tightly as possible and roll on the floor or get someone to pat you out



Emergency Spill Kit On the wall by the fume hood

•Use for a large spill, or corrosive or oxidizing substances, or if fumes are escaping to other rooms•Alert your teacher, who has received special training

First Aid Kit On the counter by the green cupboards

•Alert your teacher, who will assist you

Practice problems (Solutions):5. What should be done in the following two

scenarios? While your lab partner is boiling some water, the fire

alarm goes off. Turn off the hot plate/ Bunsen burner. Separate any chemicals that could possibly react while you’re

out of the room, then calmly leave the lab. Your lab partner has just poured some acid into what

you thought was a beaker of water. It starts to bubble rapidly.

The two chemicals are now reacting. Do not touch the beaker. Come get the teacher/ lab tech and tell them what the two

chemicals could be

Safety symbolsTwo different systems of safety symbols have

been developed to warn users of potential hazards

HSHS WHMISWhat does the acronym stand for?

Household Safety Hazard Symbols

Workplace Hazardous Materials Information

System

Where is it used? For household products (the average

consumer)

In labs & industry (people with some understanding of

chemistry)

Number of symbols 4 8

Colour coded? Yes, three shapes and colours are used to indicate degree of

hazard

No, all symbols are in circles and are

printed in black or red

HSHSHousehold Safety Hazard SymbolsCORROSIVE POISONOUS EXPLOSIVE FLAMMABLE

The product can burn your skin or eyes. If swallowed, it will damage your throat and stomach

If you swallow, lick, or in some cases, breathe in the chemical, you could become very sick or die.

The container can explode if heated or punctured. Flying pieces from the container can cause serious injury.

The product or its fumes will catch fire easily if it is near heat, flames or sparks.

HSHSdegree of hazard

CAUTION WARNING DANGER

Yellow inverted triangle Orange diamond Red octagon

LOWEST HAZARD HIGHEST HAZARD

WHMISthe Workplace Hazardous

Materials Information System is a national warning system for dangerous chemicals

WHMIS symbols are more specific than HSHS, but require a bit more understanding of chemicals

WHMIS SYMBOLSSymbol Meaning Description Examples

compressed gas

gas is under pressure and could explode

propane tank

helium tank

flammablecan burn or burst into flames if placed near a heat source or spark

natural gas

ethanol

oxidizing

reacts with oxygen,may not burn itself, but will release gases that

make a fire worse

chlorine

nitrogen dioxide


poisonous, causing

immediate toxic effects

a substance that is highly poisonous and will cause immediate

health hazards

cyanide gas

some pesticides

poisonous, causing other toxic effects

a substance that is still harmful, but will act

over a longer period of time (e.g. carcinogens

cause cancer)

gasoline fumes

cigarettes

ammonia

corrosive

can attack (corrode) metals or cause

permanent damage to human tissues on

contactburning, scarring, and blindness may result

hydrochloric acid

sodium hydroxide


dangerously reactive

may react violently under conditions of

shock or an increase in pressure or temperature

they may also react vigorously with water to release a toxic gas.

pure hydrogen peroxide

aluminium chloride

biohazard

organisms or toxins released by organisms that causes disease in

humans

bloodE. coli

bacteria

WHMIS - purposeTo ensure that all work places across Canada

that work with hazardous chemicals have a standardized way for handling and labeling toxic chemicals.

Provides:hazard identificationproduct classification

ways of safely storing and organizing chemicalslabeling methods & material safety data sheetsstandardized worker training and education

Practice problems:7. For each room listed, suggest

one hazardous chemical that might be found in it. Include the WHMIS symbol that would be appropriate for that hazard.

a) kitchen b) bathroom c) garage d) bedroom e) classroom

http://toxmystery.nlm.nih.gov/

http://toxmystery.nlm.nih.gov/

Material Safety Data SheetsMSDS are detailed

information sheets describing the particular properties, hazards, and emergency procedures for a specific chemical

Each and every single chemical in the lab has its own sheet, and they are organized into binders alphabetically

Material Safety Data SheetsInformation that can be found on the

MSDS:material’s identity (e.g. Clorox bleach)

brand name e.g. Clorox

chemical name e.g. sodium hypochlorite

common name e.g. bleach

Material Safety Data Sheetshazardous ingredients

lists ingredients as small as 1% e.g. sodium hypochlorite, 5.25%

unless listed, the rest of the substance is water

physical & chemical hazards / characteristicsstability, reactivity, flammability,

explosiveness, corrosiveness, compatibility with other materials

often listed using WHMIS symbolse.g. stable, incompatible with strong

acids, toxic, corrosive, oxidizing

Material Safety Data Sheetshealth hazards and information

acute and chronic effects e.g. corrosive, causes eye and skin burns, causes

digestive tract burns, harmful if inhaled, causes respiratory tract irritation

carcinogen? (may include human and animal summaries)

exposure limitshow it gets into the body, what organs it

targets, symptoms of overexposure e.g. route: blood; organs: eyes, skin, lungs

Material Safety Data Sheetsprecautions for handling and storing

any safety equipment required (e.g. gloves, eyewash station) or monitoring equipment

emergency and first aid procedureshow to deal with cases of inhalation, ingestion, and

eye or skin contact e.g. ingestion: do not induce vomiting

specific fire-fighting informationprocedures for cleanup and spills

identity of the organization responsible for creating the MSDS, date of issue, contact number

HomeworkSafety worksheet

A1.2Properties and Classification of Matter

Properties of matter“Matter” includes anything that has mass and

takes up spaceTo divide up this nearly infinite list of “stuff”, we

classify different types of matter based on their properties

Properties: the physical and chemical characteristics of a substancePhysical properties: appearance and composition of

a substance, can usually be determined using the five senses

Chemical properties: the reactivity of a substance, can be determined by doing an experiment

Physical propertiesProperty Description

boiling point temperature of boiling (or condensing)

melting point temperature of melting (or freezing)

malleability can be flattened into sheets without crumbling

ductility can be stretched into wires without breaking

colour colour (or colourless)

transparency clear (or opaque)

state solid, liquid, or gas at room temperature

solubility ability to dissolve (usually in water)

crystal formation

formation of crystals, appearance of crystals

conductivity ability to conduct heat or electricity

magnetism magnetic attraction between objects

Chemical propertiesProperty Description

ability to burn combustion (causing flame, heat and light)

flash point temperature needed to ignite a flame

behaviour in air tendency to break down, react, tarnish

reaction with water

tendency to corrode or dissolve

reaction with acids

corrosion, sometimes bubble formation

reaction to heat tendency to melt or decompose

reaction to red and blue litmus

blue red - acidred blue - baseno colour change - neutral

MatterPure

substancesElements

Compounds

MixturesHomogeneousSolutions

Heterogeneous

Mechanical mixtures

Suspensions

Colloids

Classification of matterPure substances Mixtures

all the particles making up the substance are identicalelements –cannot be

broken down into other substances e.g. carbon

compounds – made up of two or more elements in fixed ratios e.g. water

combination of pure substanceshomogeneous

mixtures – the separate components are not visible

heterogeneous mixtures – the separate components are visible

Classification of matterHomogeneous mixtures

the prefix “homo” means “the same”, meaning all the parts of the solution look the same

Solutionsone example of a homogeneous mixturein a solution, one substance is dissolved in

anotherthe substance dissolving is the solute and the

substance it’s dissolving in is the solvent

Classification of matterMechanical mixtures

Suspensions

The different substances are clearly visible

E.g. trail mix

The components of the mixture are in different states

E.g. mud in water, aerosol sprays

Colloids

Similar to a suspension but the suspended substance cannot easily be separated out

E.g. whole milk

Classification of matterNot every substance can be easily classified

because some substances have features of several categoriesE.g. motor oil doesn’t have constant properties

– it can separate out over time so sometimes it behaves as a solution and sometimes a colloid

Pure substances are much easier to classify because Elements are classified in the periodic tableCompounds are further classified according to

the elements that compose them

Physical change vs. chemical change

Physical change – does not alter the chemical characteristics of the substances involved, e.g. phase changes changing from solid to liquid

to gascrystallization / dissolving allowing a

substance to crystallize, then dissolve back into solution

Chemical change – the substances produced have different chemical properties than the substances that reacted

Chemical reactionsIn a chemical reaction, chemical change

occurs when:at least one new substance is formed, with new

physical and chemical properties sometimes, those new substances can be observed

with phase changes such as bubbles or precipitates sometimes, they can be observed with colour

changes or new odours,a change in energy occurs

this is often detected by a change in temperature (e.g. it gives off heat)

Homework

A1.2 – Check and ReflectPg.17 #1-7, 9

A1.3Developing Ideas about Matter

Chemistry in our worldEven before scientists fully understood the

structure of the atom or had the technology to study it, people were using chemistry in their daily livesFood chemistryMetallurgyAlchemy

Food chemistryMethods of preserving food

heating food – temporarily sterilizes it (kills the micro-organisms)

canning – heating the food, then sealing it in an air-tight container

freezing – low temperatures prevent the grown of micro-organisms

Food chemistrysalting – salt dries the water

out of the meat, but also preserves it by drying the water out of any bacteria

fermentation – bacteria naturally present on the surface of living organisms converts starches and sugars into acid, preserving the food and giving it a sour flavour

Metallurgythe science of producing

and using metalsannealing

the heating of a metal before it’s hammered, which makes it less brittle

this technique has allowed copper to be used for tools, weapons and jewellery for thousands of years

copper works better than other pure metals because of its hardness and malleability

Metallurgyother techniques

includealloys – the heating

and combination of two or metals to gain the benefits of both e.g. brass, bronze

smelting – extracting pure metal from its ore e.g. getting iron

from iron ore

Alchemyearly experiments involving

a combination of science and magic

was mostly schemes for getting rich, or producing “miracle cures” such as anti-aging serums

in the process, also resulted in:the discovery of mercurya method for the

production of acids the improvement of

glassware and lab equipment

Our understanding of the atomAccurately describing matter in terms of its atomic

structure is something that scientists are still working on today.

This section deals with the evolution of our ideas on the atom and its structure, from Aristotle (~400 BC) to today’s theory on Quantum Mechanics

As we go through each scientist’s contribution, try to identifyWhat was different about his view compared to

previous theory?How did this view contribute to our current

understanding?

Our understanding of the atomWhat you learn in

Science 10 about the actual structure of the atom is still a simplification of what we believe to be true, however we will present the Bohr model as being “close enough”.

Our understanding of the atomDifferent elements are

simply different combinations of the same three particles

What makes oxygen different than nitrogen, for instance, is that oxygen has one more of each of the particles, but an oxygen proton looks exactly the same as a nitrogen particle.

Our understanding of the atomFeatures of this

model of the atom:Protons (p+)

Positively-charged particles

Found in the nucleusNeutrons (n0)

Neutral particles Found in the nucleus Prevent the p+ from

repelling each other

Our understanding of the atomElectrons (e-)

tiny negatively- charged particles

in orbit around the nucleus

hardly have any mass (about 1/2000th that of a p+ or n0), but make up most of the volume of the atom

How did we get to this understanding?

Aristotle 400 B.C.all matter was composed of 4

elements: earth, air, water and fire

what he got right:matter is made up of different

combinations of elementselements can be divided up based

on their propertieswhat he got wrong:

only 4 elementsthe elements were “continuous”,

that is, they weren’t composed of “parts”

DRY WET

COLD

HOT

Democritus 400 B.C.

working at the same time as Aristotlematter was made up of tiny particles, called

atomos, that could not be divided into smaller pieces

what he got right:matter is composed of tiny particlesthe atoms determine the properties of the element

what he got wrong:atoms are indivisible, that is, that they aren’t made

up of any smaller parts

John Dalton early 1800sperformed experiments by combining

different elements to form new substances (compounds)

atoms are like small spheres that varied in size, mass or colour

John Dalton early 1800swhat he got right:

all matter is made of small particles called atomsall atoms of an element are identical in properties such as

size and massatoms of different elements have different propertiesatoms of different elements can combine to form

compounds with new propertieswhat he got wrong:

atoms are solid and cannot be divided any further

J.J. Thomson 1890sexperimented with beams of

particles produced in a vacuum tube

he passed electricity through different samples of elements, and found that a beam of particles was emitted when the element became “excited”

showed that the beam was made of negative charges, and that different elements produced the same type of beam

thus credited with the discovery of the electron

J.J. Thomson 1890sThe “Plum Pudding”

ModelIn Thomson’s model,

the negatively charged electrons are stuck in a sphere of positive charge

so named because it’s like raisins in plum pudding (or chocolate chips in a cookie)

J.J. Thomson 1890swhat he got right:

atoms can be further divided into smaller particles

one of those particles is the electron, which carries a negative charge

the electrons in one element are the same as electrons in another element, but in different amounts

J.J. Thomson 1890swhat he got wrong:

the electrons are stuck in the positive sphere, instead of around it

this was corrected by Japanese Scientist H. Nagaoka in 1904, who said the electrons traveled around the nucleus like Saturn’s rings

Ernest Rutherford 1890sbegun his research with

Thomson, but expanded on his ideas by discovering the nucleus

his experiment is called the Gold Foil Experiment, and was so designed: a sample of a radioactive

element was placed in a lead chamber with a tiny opening

through this opening, a beam of positively-charged particles would be emitted

these particles were traveling at a VERY high speed toward a thin sheet of gold foil

Ernest Rutherford 1890sbecause the particles were

moving so fast, and the gold was so thin, he expected the gold foil not to slow the particles down at all, and that they would pass through this would be like firing a

cannonball at a sheet of tissue paper

most of the time, this is exactly what happened, however…

once in about every 10000th time, the particle would bounce back this would be like the tissue

deflecting the cannonball – a very surprising result!

Ernest Rutherford 1890sfrom this experiment, he

realized that the gold atoms had to be made mostly of empty spacewhen the beam hit the

99.99% of empty space, it passed right through

however, 0.01% of the time, the beam struck a positive “spot” on the gold foil, which he determined to be the tiny nucleus of the atom

Ernest Rutherford 1890swhat he got right:

the nucleus is very small compared to the empty space around it

the electrons occupy some of the empty space

the nucleus has a positive charge

what he got wrong:the electrons “swarmed”

around the nucleus like bees around a beehive

Neils Bohr early 1900s

credited with discovering the orbital levels of the electrons, that is, that the electrons don’t swarm randomly, but rather occupy specific energy levels around the nucleus

he discovered this by passing electricity through different elements to excite them, then letting the electrons release that energy in the form of light

Neils Bohr early 1900s

he then noted the pattern of light bands emitted from the element

since the light emitted was related to the electrons, he reasoned that each element had a different number of electrons, and that the electrons occupied certain energy levels

Neils Bohr early 1900swhat he got right:

electrons occupy set energy levels around the nucleus

electrons cannot fall below the lowest energy level

Neils Bohr early 1900swhat he got wrong:

electrons are not actually a solid particle, but actually a cloud of negative charge – Quantum Mechanical Model

there are two types of particles in the nucleus: the proton and the neutron

Homework

A1.3 Check and Reflect (page 25)#1, 5, 6, 7

A1.0 Section Review (page 27)#3, 5, 9, 15, 17

Documents

Chapter A1 – Particles & the structure of matter