1. Atomic Structure

2. Atom Atoms are made of: Nucleus Electron shells
Makes up 99.99% of the atoms mass, but only 0.01% of the atoms volume.
Protons
Positively charged particles (p+)
Neutrons
Neutrally charged particles (n0)
Electron shells
Electrons
Negatively charged particles (e-)
Smallest particle in the atom.

3. Atomic mass Mass in AMU (atomic mass units) Mass in grams
Electrons = 0 amu (actually 1/1840)
Neutrons = 1 amu
Protons = 1 amu
Mass in grams
Electron = 9.11 x grams
Neutron = 1.67 x grams
Proton = 1.67 x grams

4. N Atomic Number 7 Main number on each element on the periodic table.
Equals the number of protons in an atom.
Nitrogen has an atomic number of 7. It has 7 protons. N 7

5. Mass Number
The mass number is equal to the number of protons plus the number of neutrons.
Mass number = protons + neutrons
Mass number on the periodic table is the average atomic mass.
Atoms may contain more or less neutrons. These are called isotopes.
The average atomic mass is an average of all the isotopes and how common they are. N 7
The average atomic mass
of nitrogen is Its
most common isotope has
a mass of 14.
7 protons + 7 neutrons = 14

6. Isotopes
Atoms of the same element can have different numbers of neutrons.
different mass numbers.
called isotopes.

7. X Symbols Mass number Atomic number
Contain the symbol of the element, the mass number and the atomic number.
Mass
number X
Atomic
number

8. Naming Isotopes Put the mass number after the name of the element.
carbon- 12
carbon -14
uranium-235

9. Na Symbols 24 11 Find the number of protons number of neutrons
number of electrons
Atomic number
Mass Number
Name 24 Na 11

10. Br Symbols 80 35 Find the number of protons number of neutrons
number of electrons
Atomic number
Mass Number
Name 80 Br 35

11. Practice: Fe 30 5 11 20 21 Cu 29 65 Element name Symbol Atomic #
# of Protons
# of Electrons
# of Neutrons
Mass number Fe 30 5 11 20 21 Cu 29 65

12. Electrons = protons - charge
The number of electrons in a neutral atom is equal to the number of protons.
In an ion, the number of electrons is equal to the protons minus the charge.
Electrons = protons - charge

13. Valence Electrons Electrons in the outer most shell.
All atoms want 8 valence electrons.
They can either lose the electrons they have, or gain extra electrons.
They do this by bonding with other atoms.
The number of valence electrons are determined by the column on the periodic table.

14. Valence Electrons 1 Valence electron 8 Valence electrons
Valence electrons of the
Transition metals vary

15. Dot Notation
Dot notation shows the valence electrons placed around the symbol of the element.
The electrons are placed in the following order. 3 6 X 4 1 7 2 5 8

16. . : : S . For Example Sulfur: Try the following: Aluminum Chlorine
Arsenic

17. Electron Configuration
Electron configuration shows the energy level and orbital of every electron in an atom.
The energy levels are known by the rows on the periodic table.

18. Energy Levels 1st energy level 2nd energy level 3rd energy level
4th energy level
4th energy level
5th energy level
6th energy level
7th energy level
4th energy level
5th energy level

19. Orbitals
Orbitals are the shaped areas where the electrons are found.

20. S P D F Orbitals S orbital can hold 2 electrons
P orbital can hold 6 electrons
D orbital can hold 10 electrons
F orbital can hold 14 electrons S P D F

21. Example The electron configuration for Bromine:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
Use the periodic table to write the electron configuration.
Try the following:
Nitrogen
Calcium
Cesium

22. Bohr Models The Bohr model is a visual representation of the atom.
The protons and neutrons are written as the nucleus of the atom.
The electrons are placed around the nucleus using the electron configuration.
Let me show you.

23. Maximum electrons The first energy level can hold 2 electrons
The second holds 8
The 3rd holds 18
The fourth holds 32
The 5th holds 32

24. Molar Mass First look at the formula for the compound.
Multiply the number of each atom by the mass of each atom.
The sum of the masses will be the mass of the compound (molar mass)
Example:
CaF2
= 40.1
= 38.0
Molar mass = 78.1

25. Practice What is the molar mass of the following compounds?
Sodium chloride
58.5
Magnesium Bromide
184.1
Carbon dioxide
44.0
Aluminum sulfate
342.3
Al2(SO4)3
= 54.0
= 96.3
= 192.0
Molar mass = 342.3