1. ATOMIC STRUCTURE
8A1 ALYSSA

2. ATOM
What Is an Atom?
An atom is the basic unit of an element. An atom is a form of matter which may not be further broken down using any chemical means. A typical atom consists of protons, neutrons and electrons.

3. What is helium ? HELIUM ATOM
Helium is the name for the element with atomic number 2 and is represented by the symbol He.
It is a member of the noble gases group.
What is helium ?
Shell N - +
proton N + -
neutron
electron
This is helium atom

4. number of electrons = number of protons
HELIUM ATOM He 2
Atomic number
The number of protons in an element.
Examples: The atomic number of hydrogen is 1; the atomic number of carbon is 6.
Also Known As: The atomic number is also known as the proton number. It may be represented by the capital letter Z. 4
Atomic mass
the number of protons and
neutrons in an atom
number of electrons = number of protons

5. ATOMIC STRUCTURE
Electrons are arranged in Energy Levels or Shells around the nucleus of an atom.
first shell: a maximum of 2 electrons
second shell: a maximum of 8 electrons
third shell: a maximum of 8 electrons

6. 1.Electronic Configuration
ATOMIC STRUCTURE
There are two ways to represent the atomic structure of an element or compound:
1.Electronic Configuration
2.Dot & Cross Diagrams

7. ELECTRONIC CONFIGURATION
With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example:
Helium
configuration = 2 2
2 in 1st shell He 4

8. He DOT & CROSS DIAGRAMS Helium
With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example:
Helium He 2 X He X 4

9. SUMMARY The Atomic Number of an atom = number of
protons in the nucleus.
The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
The number of Electrons = Number of Protons. .
4. Each shell can only carry a set number of electrons.

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