Atoms, Elements, Periodic Table, Compounds, Mixtures

Section 1: Atoms

ATOMS:

1)An atom is the smallest part of an element that still has the properties of that element.

(the smallest part of “stuff” that is still “stuff”)

2)Parts of an Atom:

a) nucleus: made of protons and neutrons

b) electron cloud: composed of electrons and empty space

nucleusElectron cloud

3)Particles that make up an atom:a) protons: positively chargedb) Electrons: negatively chargedc) Neutrons: NO charge (neutral)

Two hydrogen atoms are walking along the street. One suddenly goes: - Oh shoot, I´ve lost an ' electron! Other one says: -Are you sure? –

Yes, he replies.- -I'm positive.

4) Atoms differ from one another because of the number of protons in the nucleus.

-this is called the atomic number

(all atoms with the SAME atomic number belong to the same element)

5) Isotopes: atoms of the same element, with a different number of neutrons.

Tell me . . .1) What are the three particles that make up an atom?

2) What is the center of an atom called?

3) What makes one type of atom different from another?

6) The number of protons in an atom added to the number of neutrons gives what is called the mass number.

If you take the mass numbers of all the different isotopes that exist, and average them together, you get what is called the Atomic mass.

Atomic number

Atomic mass

Elements

1)An element is a pure substance that cannot be broken down into

simpler substances by physical or chemical means.

All atoms of the same atomic number are of the same element.

2) A pure substance is one that has only one type of particle.

Elements and Compounds are both pure substances.

3) Elements can be identified by their characteristic properties:•remember those?

properties that don’t change no matter the size of the substance

things like boiling point, melting point, density and reactivity

Explain how an element is different from an atom.

Are characteristic properties physical or chemical or both?

1) Elements are organized on the Periodic Table of Elements by atomic number.

2) Periodic Table-columns are called groups or

families (because they behave in a similar fashion)

Rows are called periods: Elements show a gradual change in properties across a period.

2) Periodic Table – cont:

3) Elements are grouped into three categories based on similar properties:metals, non-metals, Metalloids

4) metals: shiny, good conductors, malleable, and ductileEx: iron, aluminum

Iron filings

5) Nonmetals: dull, poor conductors, brittleEx: carbon/graphiteSulfurNoble gases

Argon is used in light bulbs

Neon

sulfur

6) metalloids: properties of bothcalled semiconductors

Ex: silicon

This has nothing to do with metalloids – it just amused me.

If you know the category, you know the properties, and for an unknown element, if you know the properties you can figure out the category.

Name the three categories of elements found on the Periodic Table.

How are periods and Rows on the Periodic Table different?

Section 2: compounds

1) A compound is a pure substance composed of two or more elements that are chemically combined.

Ex: water, salt

Compounds are considered pure, because each particle of NaCl is identical to every other particle of NaCl

2) Compounds are created through a chemical change and can be broken down through a chemical change

What is the difference between anelement and compound?

What can compounds be broken down into?

3) Elements in a compound are combined in a specific ratio.

All the particles are the same so it is a pure substance

Carbon dioxide (CO2) will always have 2 atoms of oxygen for every one atoms of carbon

Molecule

4) A molecule is a neutral group ofatoms held together by covalentbonds (nonmetals bond with non metals

sharing electrons)Example-water H20

5) Chemical Formulas• A chemical formula is a shorthand notation for a

compound or a diatomic element using chemical symbols and numbers.

• A chemical formula indicates the chemical makeup by showing how many of each kind of atom is present in a molecule. Ex: H20 is the chemical formula for water

• H2O

Element oxygenSubscript number 2

Elementhydrogen

What does the numbers in theformula H2O2 tell you about thisformula?

What does H mean?

What does O mean?

Section 3: Mixtures

 

1) A mixture is a combination of two or more substances that are not chemically combined.

Video link

Properties

2) Substances in a mixture retain their identities.

3) Mixtures can be physically separated• Ex: picking off the pepperoni on your pizza

Properties

4) Some mixtures are harder to separate than others because you don’t always see all of the materials in that mixture.

• Example: salt water

Properties

5) Mixtures do not have definite ratios • Ex: air is a mixture• 78% Nitrogen• 21% Oxygen• 1% other gases

6)Types of Mixtures

• Two types of mixture:• Homogeneous mixture-mixed the same

throughout (milk)• Heterogeneous mixture-mixed differently

throughout (Italian dressing)

7)Techniques for Separating Mixtures

• Mixtures are physically separated here are some common techniques

• Distillation• Magnet• Centrifuge

8)The common types of mixtures:a) solutionsb) suspensionsc) colloids

What is the difference between acompound and mixture?

Name three techniques you can useto separate mixtures.