Atomic Structure

Question 1

Define the word element.

Answer 1

An element is a substance that is made up of only one kind of atom.

Question 2

Describe the basic structure of an atom.

Answer 2

Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in shells.

Question 3

Explain in detail the differences between pure elements, compounds and mixtures.

Answer 3

• element is a pure substance which contains identical atoms or molecules with only one type of atomic core.
• compound is a pure substance which contains identical molecules with two or more types of atomic core.
• mixture is a material which has two or more types of molecules.

Question 4

Explain the significance of chemical symbols used in formulae and equations.

Answer 4

Symbols help simplify the process of identifying and explaining chemical formulas. For instance, the compound water is composed of two atoms of hydrogen and one atom of oxygen. The formula for the same is H2O.

Question 5

What is potassium hydroxide + sulfuric acid in a word equation?

Answer 5

Potassium sulfate + water

Question 6

Explain why mass is conserved in a chemical reaction.

Answer 6

The law of conservation of mass states that no atoms are lost or made because mass cannot be created or destroyed in a chemical reaction.

Question 7

Justify in detail how mass may appear to change in a chemical reaction.

Answer 7

If a gas escapes, the total mass will look as if it has decreased. If a gas is gained, the total mass will look as if it has increased. However, the total mass stays the same if the mass of the gas is included.

Question 8

How to state that mass is conserved in a chemical reaction.

Answer 8

The total mass of the reactants in a chemical reaction is equal to the total mass of the products.

Question 9

List the significant models proposed for atoms.

Answer 9

• Dalton’s atomic model
• Thomson’s atomic model
• Rutherford’s atomic model
• Bohr’s atomic model
• The quantum atomic model

Question 10

Describe the differences between the plum-pudding and the nuclear model of the atom.

Answer 10

In the plum pudding model, there is a positive sphere with negative charge randomly placed within the sphere. There is no empty space. In the nuclear model, there is a central positive, tiny nucleus, with mostly empty space and lots of negative charges a long way from the nucleus.

Question 11

Justify why the model of the atom has changed over time.

Answer 11

The atomic model has changed over time due to advancements in technology and scientific understanding e.g the discovery of the electron.

Question 12

Identify the key parts of the plum- pudding model and the nuclear model of the atom.

Answer 12

• The plum pudding model has a positive sphere with negative charge randomly placed within the sphere, there is no empty space.
• The nuclear model has a central positive, tiny nucleus, with mostly empty space and lots of negative charges a long way from the nucleus.

Question 13

Explain how evidence from scattering experiments changed the model of the atom.

Answer 13

An alpha particle scattering experiment was carried out where alpha particles were directed at gold foil. Most of the alpha particles passed straight through showing the atom was mostly empty space, a few alpha particles deflected at large angles, so the mass is concentrated at the centre of the atom (the nucleus)

Question 14

Evaluate the current model of an atom.

Answer 14

The modern atomic model represents atoms containing a nucleus of protons and neutrons and a vague gradient or cloud surrounding it containing the electrons

Question 15

State the relative charges and masses of subatomic particles.

Answer 15

Subatomic particles - Relative mass - Relative charge

Proton - 1 - +1

Neutron - 1 - 0

Electron - 1/2000 - -1

Question 16

Describe atoms using the atomic model.

Answer 16

The atomic model consists of a nucleus containing protons and neutrons, surrounded by electrons in shells. The numbers of particles in an atom can be calculated from its atomic number and mass number.

Question 17

state that atoms have no overall charge.

Answer 17

they contain equal numbers of positive protons and negative electrons.

Question 18

Recognise and describe patterns in subatomic particles of elements listed in the periodic table.

Answer 18

As you move from left to right across the periodic table, atoms have more electrons in their outer energy level and more protons in their nucleus. The greater attraction between the increased number of protons (increased nuclear charge) and electrons, pulls the electrons closer together, hence the smaller size.

Question 19

Explain why we can be confident that there are no missing elements in the first 10 elements of the periodic table.

Answer 19

Since protons cannot be split, there cannot be any unknown elements within the periodic table as we now know it.

Question 20

What is an ion

Answer 20

An ion is an electrically charged atom or group of atoms formed by the loss or gain of electrons. Negative ions are called anions and form when atoms gain electrons, meaning they have more electrons than protons.

Question 21

Describe isotopes using the atomic model

Answer 21

Atoms of the same element with different numbers of neutrons are called isotopes

Question 22

Why does an ion have a charge?

Answer 22

An ion is an atom or molecule that has a different number of electrons than protons, so it has a charge.

Question 23

How much smaller is the nucleus than the atom?

Answer 23

Approximately 100,000x smaller

Question 24

why does chlorine not have a whole mass number

Answer 24

chlorine contains two different isotopes

Question 25

state that electrons are found in energy levels of an atom.

Answer 25

electrons fill the lowest energy level first before moving to higher energy levels.

Question 26

What are the maximum number of electrons in the first three energy levels.

Answer 26

2,8,8

Question 27

explain why elements in the same group react in a similar way

Answer 27

The elements in the same group have a similar number of valence electron.

Question 28

Make predictions for how an element will react when given information on another element in the same group.

Answer 28

If you know what one of the elements in a group is like, you can make predictions about the other elements in a group. For example, all the elements in group 1 are reactive metals, and all the elements in group 0 are unreactive non-metals.