Diagramming Atoms

Labeling Electrons – Part 1Supplement to Book – Glencoe: Chapter 22 and 19-3

First a bit of Review!

• Atomic number – number of protons in the nucleus of an atom

• Mass number – number of protons + number of neutrons in the nucleus of an atom

Atomic Diagrams• Electron shell diagrams are ways to

visualize the arrangement of electrons in an atom

• These diagrams

show which energy

levels, called shells,

the electrons are

found.

Electron shell diagrams Particle locations

1. Nucleus

- All protons (p+)

are found in

the nucleus

- All neutrons (N)

are found in

the nucleus

Electron shell diagrams2. Electron Cloud

- The general space around an atom where the electrons are found

- All electrons (e-)

are found in the

electron clouds

in orbitals

Electron shell diagrams3. Neutral atoms of any element have

equal numbers of protons and electrons

4. The number of neutrons can be found

from the atomic mass of an element - Round atomic mass to the nearest whole number

mass number

- Mass number = Atomic number + neutron number

Energy levels in atoms

Quantum Numbers – values which represent the theoretical “address” of an electron in an atom

1. Electrons are modeled in atoms combining two atomic models

Bohr’s Model

• Electrons

orbit the

nucleus

in fixed

paths

Modern Atomic Model

• Electrons

are found

in areas

called

electron

clouds

Energy levels in atoms 2. There are distinct energy levels in an atom

“n” number (this is the first quantum number)

• Energy levels – specific regions of space in which electrons can move about the nucleus of an atom, based on stability of the atom

Energy Level Numbera. “n” can equal

1, 2, 3, 4, 5, 6, or 7

b. Only whole, n = 1

non-negative

numbers

c. Like the rungs

of a ladder n = 2

*There is nothing n = 3

between the energy levels but open space

Energy levels in atoms 3. Energy level numbers generally

correspond to period number (there is a pattern to it)

Energy levels in atoms

n # 1 2 3 4 5 6 7

Max

e-

2 8 18 32 32 32 32

4. Each energy level may contain only a specific maximum number of electrons

Energy levels in atoms5. Energy levels fill

up in a specific order

lowest energy (n = 1)

(most stable)

to

highest energy (n = 7)

(least stable)