Atomic Structure

1
Atomic Structure

• 8th Grade Science

2
Parts of an Atom

• Protons positive charge 1
• Neutrons do not have a charge (0)
• Electrons negative charge 1-
• Atoms of different elements differ in the number
  of protons they contain.
• Atomic Number number of protons and number of
  electrons in a neutral atom Identifies the
  element!

3
A little joke

• A neutron walked into a restaurant and asked how
  much for a drink. 
• The bartender replied,  "for you, no charge." 
• -Jaime - Internet Chemistry Jokes

4
All atoms have 2 common structures
nucleus
energy level(s)
5
Each structure is made of subparticles.
energy level
protons
nucleus
electrons
neutrons
6
Energy Levels

• 1st shell can hold 2 electrons
• 2nd shell can hold 8
• 3rd shell can hold 18

7
Electron Cloud

• Protons and Neutrons are found in a small,
  positively charged () center of the atom called
  the nucleus that is surrounded by a cloud
  containing electrons.

8
Atomic Mass Unit (AMU)

• The mass of a proton or neutron is about 1 atomic
  mass unit or AMU
• Proton 2000 times larger than an electron.
• The electron cloud makes most of an atoms
  volume (space). Electrons are very tiny.
• A neutron is large and heavy like a proton.

9



1926
10
If both protons and neutrons are found in the
nucleus, why is it positive?

1. Neutrons have a positive charge
2. Both neutrons and protons have a positive charge
3. Protons have a positive charge and neutrons have
   no charge
4. Neutrons have a negative charge

11
Atomic Structure VideoDiscovery Education
12
The number of protons in the nucleus of an atom
is that atoms atomic number.
Carbon has 6 protons. The atomic number of
carbon is 6.
The number of protons plus the number of neutrons
in the nucleus of an atom is its atomic mass.
13
How many protons are in Magnesium?

1. 25
2. 24.31
3. 11
4. 12

14
What is the atomic mass of Potassium?

1. 39.10
2. 19
3. 15
4. 30.97

15
To find the number of neutrons in an atom,
subtract the atomic number from the atomic mass.
16 Atomic mass (protons neutrons) - 8 Atomic
number (protons) ___ 8 Number of neutrons
16
A Little Saying to help you remember

• A
• P
• E

• M
• A
• N

tomic
ass
rotons
tomic
lectrons
uetrons
17
8
Atomic Number
8
Protons
16
Atomic Mass









8
Neutrons
2
Energy Levels
oxygen atom
8
Electrons
18
What is the number of neutrons in Potassium?

• 39
• 19
• 20
• 21

19
How many neutrons are in Lithium?

• 3
• 4
• 6
• 7

20
Valence Electrons

• Electrons farthest away from the nucleus or most
  loosely held.
• Ranges from 1 to 8 valence electrons
• Many properties of the atom, and therefore of an
  element, are determined by the number of valence
  electrons.

• http//www.tutorvista.com/content/science/science-
  i/structure-atom/valence-shell-electron.php

21
Electron Dot Diagrams

• Also called Lewis Structure
• Used to represent valence electrons
• Made up of the element symbol surrounded by dots
• Each dot stands for one valence electron

22
Chemical Bonds

• Valence electrons can form chemical bonds, a
  force that holds atoms together.
• When bonds form, valence electrons are either
  transferred or shared between atoms.
• When atoms end up with 8 or 0 valence electrons,
  they become more stable or less reactive.