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CHEM LESSON 3ATOMS AND ELEMENTS

DO-NOW

What are the three parts of an atom called?

Atoms and Elements

Each element consists of atoms that differ from the atoms of other elements.

An element can be identified by the number of protons in the nucleus.

Atoms and Elements

In the nucleus of the atom, the protons and neutrons are held together by a strong force

Atoms and Elements

Every atom of an element as the same number of protons. We call this the atomic number.

For example, every atom of carbon has 6 protons

Atoms and Elements

Atomic Number is the number of protons in the nucleus for each element.

Oxygen’s atomic number is 8, Iron’s atomic number is 26.

Atoms and Elements

The Atomic Mass is the average mass of an atom for that specific element

Example: Oxygen’s atomic mass is 15.99 and Iron’s atomic mass is 55.847

Atoms and Elements

The atomic mass, atomic number, and the chemical symbol are all organized into a square for each element on the periodic table.

Atoms and Elements

Atomic Number Chemical

Symbol Element Atomic Mass

Atoms and Elements

Electrons are found in an electron cloud surrounding the nucleus.

Atoms and Elements

Electrons are arranged on shells. Shells are the different energy levels on which electrons are found

Electron Shells

The inner most shell can only hold 2 Electrons

The second shell can hold 8 Electrons

The third shell can hold 8 Electrons

Periodic Table

The Periodic Table is how scientists have organized all of the elements.

Periods

1st period: 1 shell 2nd period: 2 shells 3rd period: 3 shells 4th period: 4 shells

• Each row is called a “period”

• The elements in each period have the same number of shells

Groups

Group 1: 1 Electron Group 2: 2

Electrons Group 3: 3

Electrons Group 4: 4

Electrons Ect. All the way up

to group 8: 8 electrons.

• Each column is called a “group”• Each element in a group has the same number of valence electrons• Valence electrons are electrons in the outer shell

3, 4, 5, 6, 7

1, 2

8