Chemistry Chapter 3- Atoms: The Building Blocks of Matter

Law of Conservation of Mass:

Mass is neither created nor destroyed during ordinary chemical reactions or physical changes.

Law of Definite Proportions:

A compound contains the same elements in exactly the same Proportions regardless of sample size or source of the compound.

Law of Multiple Proportions:

If two or more compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is a ratio of small whole numbers.

Dalton’s Atomic Theory:

1.) All matter is composed of atoms—(still true; part of modern Atomic Theory)

2.) Atoms of given element are identical in size, mass, & more. Atoms of different elements differ in these traits—(part true)

3.) Atoms CANNOT be subdivided/destroyed—(part true)

4.) Atoms of different elements combine in simple whoe-number ratios to form chemical compounds—(true; modern atomic theory)

5.) In chemical reactions atoms are combined, separated, and rearranged—(true; modern atomic theory)

What experiment by Thomson discovered the electron?

Cathode ray tube

What experiment by Rutherford discovered the nucleus?

gold foil experiment

Proton:

Location: Nucleus

Charge: +

Mass: 1u

Neutron:

Location: nucleus

Charge: 0

Mass: 1u

Electron:

Location: electron cloud (outside of nucleus)

Charge: —

Mass: 0u

What keeps the nucleus together and structurally sound?

nuclear strong force

Isotopes have a different number of _________ but have the same number of ____________.

neutrons; protons

All atoms of the same element have the same number of which subatomic particle?

protons

How does the average atomic mass compare to the mass of an atom (mass number)?

Average atomic mass accounts for ALL known isotopes of an element which creates a calculated decimal. Mass number only represents one atom at a time — so it is a whole number.