Chapter 2 (Part 1): Early Atomic Theory

Learing during October

Law of Conservation of Mass

This law states that matter cannot be created or destroyed during a chemical reaction

What is each element made of?

Tiny particles called atoms

What are chemical reactions?

The reorganization of atoms

True or false: The atoms of any given element are identical

TRUE

What do objects with the same charge do?

Repel

What do atoms with opposite charges do?

Attract

True or False: objects can be charged by being rubbed against other objects

TRUE

What did the scientist J.J. Thomson do?

He studied electric discharge using cathode ray tubes(when high voltage is applied to a tube-a cathode ray is produced)

-He discovered that the ray was produced at the negative electrode and that it was repelled by the negative pole of an applied electric field(or magnetic field)→ THESE WERE ELECTRONS

-he then created the plum pudding model

Why was the plum pudding model inaccurate?

It was inaccurate because it only consisted if a cloud of positive charge and random negative electrons embedded throughout(didn’t include a nucleus)

Nucleus

The center of an atom(contains protons and neutrons)

Protons

positive charge and the atomic number

Number of protons=number of electrons

change the proton= change the element

True or False: Atoms are mostly made up of empty space

TRUE

What is the atomic number?

The number of protons and also how you classify an element

How can you find the number of neutrons?

The atomic mass(at the top) minus the number of protons(atomic number-at the bottom)

True or False: An atom is always charged

False! An atom is typically neutral(because the number of protons(+) and electrons(-) should be equal*

*if they are not the particle could be an ion

To get the correct charge of an atom what do you do?

Protons-electrons=correct charge

Groups on the periodic table are also known as

columns

Periods on the periodic table are also called

rows

where can you find electrons?

In the space surrounding the nucleus(protons and neutrons)

True or false:You can find out how many shells an element has by looking at what period(row) it is in

TRUE

How do you fill up the energy shells of an element?

You start with the lowest energy shell(closest to the nucleus) and work outward.

What are the rules for filling up the energy shells of an atom?

1. The first shell only holds 2 electrons

2. Shell 2 will hold up to 8 electrons

3. Shell 3 also holds up to 8 electrons

4. After the 3rd shell is full, the element may hold up to 20 electrons

valence electrons

the electrons in the outer shell of an atom