Atomic Number

Number of Protons

Mass Number

Number of Protons + Neutrons

C-12 or carbon-12

12 is the mass number.

12C

Left Superscript = mass number

6

12C

Left Subscript = atomic number

6

80Br

35

35

Atomic Number = ?

20Ne

20

10

Mass Number = ?

238U

238

92

Mass Number = ?

27Al

27

13

Mass Number = ?

40Ca

20

20

Atomic Number = ?

19F

9

9

Atomic Number = ?

U-235

Mass Number = 235Atomic Number = 92 (Look up!)

Mass Number? Atomic Number?

C-14

Mass Number = 14Atomic Number = 6 (Look up!)

Number of neutrons = 14 - 6 = 8

How many neutrons?

Isotope

Atoms of the same element with a different # of neutrons

Isotope

Atoms with the same atomic # but different mass #

Characteristics of Proton

Charge = +1, mass = 1 amu, location = inside nucleus

Characteristics of Neutron

Charge = 0, mass = 1 amu, location = inside nucleus

Characteristics of Electron

Charge = -1, mass = 1/1836 amu or 0.0005 amu, location =

outside nucleus

Ion

An atom that has gained or lost electrons & so carries

charge

Nucleons

Protons & Neutrons

atom

Smallest bit of an element that retains the properties of the

element.

atom

Electrically neutral. # of protons = # of electrons.

Charge

# protons - # electrons

# of neutrons

Mass number – atomic number

14C

8

6

# of neutrons = ?

9Be

5

4

# of neutrons = ?

40Ar

22

18

# of neutrons = ?

15N

8

7

# of neutrons = ?

24Mg

Right superscript = charge

12

2+

24Mg

10 electrons

12

2+

# of electrons?

86Rb

36 electrons

37

1+

# of electrons?

127Te

53 electrons

52

1-

# of electrons?

32S

18 electrons

16

2-

# of electrons?

20F

9 protons, 11 neutrons, 10 electrons

9

-

# of protons, neutrons, electrons?

Cation

Positive ion: atom lost electrons

Anion

Negative ion: atom gained electrons

Avg. Atomic Mass

Weighted avg. of masses of naturally occurring isotopes of

an element.

2 isotopes of Cl: 75% Cl-35 & 25% Cl-37.Calculate avg. atomic mass.

Avg. atomic mass = .75(35) + .25(37) = 35.5 amu

Dalton’s Model

Billiard Ball Model

Thomson’s Model

Plum Pudding Model

- --- -

++

+ ++

Rutherford’s Model

Nuclear Model

+-

- -

Rutherford’s ExperimentSource: http://www.dlt.ncssm.edu/TIGER/chem1.htm#atomic

Rutherford’s Experiment: Results

1) Most of the alpha particles went straight through. Most of the atom is empty space.

2) Some of the alpha particles were deflected back. The nucleus was tiny, but contained most of the mass of the atom.

Bohr’s Model

Planetary Model

Schrodinger’s Model

Modern or Quantum Mechanical Model

Source: http://www.dlt.ncssm.edu/TIGER/chem1.htm#atomic

Modern Model (Schrodinger or Quantum Mechanical Model)

Electron treated as a wave.Never know exactly where it is.

Bohr Configuration

Ground state configurations found in reference tables.Cannot be predicted.

Bohr Configuration of Na = 2-8-1

2 electrons in energy level 18 electrons in energy level 21 electron in energy level 3

Bohr Diagram of Na

+11

Valence Electron(s)

Electron(s) in outermost orbit or shell

Kernel

Nucleus + all innershell electrons: Everything except the valence

electrons

Bohr Model

Electrons are restricted to specific orbits or shells or principle energy levels.Each shell holds a specific # of electrons.Each shell has a specific energy & radius.Energy of electron must match energy of shell.

Maximum Capacity of Bohr Levels

Shell # Max # of electrons1234n

28

18322n2

Ground State

Bohr modelEvery electron is in the lowest available orbit.

2-8-7

Ground state configuration of Cl

2-6

Ground state configuration of O

Ground state configuration of Kr?

2-8-18-8

Principle Energy Level?

Shell #

Excited State

Bohr modelAn electron has absorbed heat, light, or electrical energy and moved to a higher energy level.Unstable. Returns to ground state quickly by emitting a photon.

2-5-1

An excited state of O

2-0-1

An excited state of Li

Continuous Spectrum

Spectrum produced by holding a prism in sunlight. Contains light at every wavelength.

Rainbow

Bright Line Spectrum

Visible light produced by electrons in atom returning to ground state: light of only a few wavelengths is present.

Each element has a unique bright line spectrum. Used to identify elements.

Wavelengths of bright lines correspond to difference between energy levels.

Source: http://www.dlt.ncssm.edu/TIGER/chem1.htm#atomic

Absorbtion of Energy

h Ground state

Excited state

E1

E2

E3

Emission of Energy

h

Ground state

Excited state

E1

E2

E3

Orbital

Modern ModelRegion of space that holds 2 electrons.Has a specific energy. Shapes vary.

E1

E2

Represents an electron dropping to a lower energy level, releasing energy in the process.