Atoms

Question 1

Define the term Matter

Answer 1

Matter is anything that has mass and volume and takes up space. It is usually found in one of the states of matter - solid, liquids and gasses.

Question 2

Define the term atom

Answer 2

Atoms are the basic unit of all matter, consisting of a dense central nucleus which contains protons and neutrons, and surrounded by a cloud of negatively charged electrons. Each atom has a different number of these sub-atomic particles which makes it different from other atoms. Each atom has an equal number of protons and electrons which makes it “neutral”.

Question 3

Summarise the development of the atomic model

Answer 3

1. Dalton proposed atoms as indivisible particles with unique properties.
2. Thomson’s “plum pudding” model suggested electrons embedded in a positive sphere.
3. Rutherford’s experiment led to the nuclear model with a dense nucleus and orbiting electrons.
4. Bohr introduced specific electron orbits around the nucleus.
5. Schrödinger and Heisenberg’s quantum mechanics replaced fixed orbits with probability-based electron clouds.
6. Modern atomic theory combines these ideas, describing atoms with a nucleus of protons and neutrons, surrounded by electron clouds in specific energy levels.

Question 4

Recall the names of the scientist who made major contributions to the development of the atomic model

Answer 4

1. John Dalton
2. J.J. Thomson
3. Ernest Rutherford
4. Niels Bohr
5. Erwin Schrödinger
   6.Werner Heisenberg

Question 5

Identify the subatomic particles within an atom and state their charges

Answer 5

There are three sub-atomic particles that make up atoms:

• Protons - positively charged and found in the nucleus
• Neutrons - No charge (neutral) and found in the nucleus
• Electrons - Negatively charged and found on outer electron shells of the atom (they are spinning very fast around the edge of the atom)

Question 6

Describe the structure of an atom and where each sub-atomic particle can be found

Answer 6

The nucleus (centre of the atom) contains protons (positively charged) and neutrons (no charge). The outermost regions of the atom are called electron shells and contain electrons (negatively charged).

Question 7

Explain what the Octet rule is

Answer 7

Each shell of an atom can hold a maximum number of electrons.

First shell: Maximum of 2 electrons
Second shell: Maximum of 8 electrons
Third shell: Maximum of 8 electrons

Electrons will fill the shells nearest the nucleus first.

The outermost shell of any atom is called the valence shell and the electrons that are in the valence shell are called valence electrons.

Question 8

Mass and charge of Protons, Neutrons and electrons

Answer 8

• Protons have a mass of about 1 amu (one of the heavier pieces of the atom)
• Protons have a +1 charge- they wouldn’t be able stick together if not for neutrons
• Neutrons no not have any charge. Through forces other than force attractions, they are able to hold the protons together in the nucleus
• Neutrons have about the same mass as protons, making them a major contributor to the mass of the atom