Atomic Structure

Chemistry 11

Ms. McGrath

Contributions to the Atomic Theory

https://www.youtube.com/watch?v=IO9WS_HNmyg

Contributions to the Atomic TheoryAristole

Believed matter consisted of:

1. Earth

2. Water

3. Air

4. Fire

5. Aether

Contributions to the Atomic TheoryDalton

Developed Atomic Theory

1. All matter is composed of atoms

2. Atoms cannot be created or destroyed

3. All atoms of the same element are identical

4. Chemical reactions occur when atoms are rearranged

5. Compounds are formed by the combination of two or more different kinds of atoms

Contributions to the Atomic TheoryThomson

• Atoms could be divided

• Discovered electrons

• Revised atomic theory to include electrons

• Created “Plum Pudding” model (thought electrons were embedded in atom)

Contributions to the Atomic TheoryRutherford

• Discovered protons

• Believed there was a massive, positively charged particle in the center of the atom

• Electrons circle the center particle

• Atoms are composed of mostly empty space

Contributions to the Atomic TheoryBohr

• Transition to modern view of atom

• Electrons travel around the atom in discrete energy level – “Bohr model”

• Electrons can move up energy levels if proper energy is applied

• This amount of energy is “Quantum” of energy

Contributions to the Atomic TheorySchrodinger

• Discovered where electrons are located

• Because electrons move in “waves” we cannot specifically pinpoint where electrons are located

The AtomComplete the following table

Electrons

• Electrons are located in “shells” orbiting the nucleus (which contains the protons and neutrons)

• Electrons located in the outer shell are called valence electrons

• The number of valence electrons can be determined by the group number (vertical columns of the periodic table) where the element is located

Valence Electrons

Identify the number of valence electrons for the following elements:

a) chlorine f) lead

b) Helium g) antimony

c) indium h) selenium

d) strontium i) arsenic

e) rubidium j) xenon

Atomic StructureComplete the following table based on the relationship between the headings (assume

atoms are neutral):Element

nameAtomic number

Mass number

Number of

protons

Number of

electrons

Number of

neutrons

a) b) 108 c) 47 d)

e) f) g) h) 42

i) 35 j) k) l) 45

m) 79 179 n) o) p)

q) r) s) t) 50 69

Ions

Ions are atoms that have gained or lost electrons – in order to satisfy the octet rule (eight valence electrons – hydrogen and helium being exceptions)

Cations – positively charged ions. These atoms have lost electrons.

Anions – negatively charges ions. These atoms have gained electrons.

Ions

For each of the following ions, indicate the number of protons and electrons.

a) lithium ion, Li+

b) calcium ion, Ca2+

c) bromide ion, Br-

d) sulfide ion, S2-

Atomic SymbolismComplete the following table

Symbol Mass # # of p+ # of n0 # of e- Overall Charge

# of valence e-

Outermost occupied energy level

Mg2+ 25

9 10 10

39 20 0

Y 89

18 25 18

7 3 2