Atomic Structure and The Periodic Table

Question 1

What is an atom?

Answer 1

The smallest part of an element that can exist.

Question 2

What is a compound?

Answer 2

They contain two or more elements that are chemically combined.

Question 3

What is a mixture?

Answer 3

Two or more elements or compounds not chemically combined.

Question 4

What are the five methods of separating mixtures?

Answer 4

Filtration, crystallisation, simple distillation, fractional distillation and chromatography.

Question 5

How is the atoms structured?

Answer 5

It has electrons in the outer shell surrounding the nucleus; containing neutrons and protons.

Question 6

What is the ‘plum pudding’ model of the atom?

Answer 6

The atom is a ball of positive charge with negative electrons embedded in it.

Question 7

1. What was John Dalton’s interpretation of the atom (1803)?

Answer 7

He used an Ancient Greek idea of atoms being indivisible, those of a given element are identical, and compounds are combinations of different types of atoms.

Question 8

What was correct about John Dalton’s concept of the atom?

Answer 8

He recognised atoms of a particular element differ from other elements.

Question 9

What was incorrect about John Dalton’s concept of the atom?

Answer 9

Atoms aren’t indivisible. They’re composed from subatomic particles.

Question 10

2. What was J.J. Thomson’s interpretation of the atom (1904)?

Answer 10

He discovered electrons in atoms in 1897, for which he won a Nobel Prize, and produced the ‘plum pudding’ model of the atom.

Question 11

What was correct about J.J. Thomson’s interpretation of the atom?

Answer 11

He recognised electrons as components of atoms.

Question 12

What was incorrect about J.J. Thomson’s interpretation of the atom?

Answer 12

Atoms have a nucleus.

Question 13

3. What was Ernest Rutherford’s interpretation of the atom (1911)?

Answer 13

He fired positively charged alpha particles at a thin sheet of gold foil. Most passed through with little deflection, but some deflected at large angles. This was only possible if the atom was mostly empty space, with the positive charge concentrated in the centre: the nucleus.

Question 14

What was correct about Ernest Rutherford’s interpretation of the atom?

Answer 14

He realised that positive charge was localised in the nucleus of an atom.

Question 15

What was incorrect about Ernest Rutherford’s interpretation of the atom?

Answer 15

It did not explain why electrons remain in orbit around the nucleus.

Question 16

4. What was Niels Bohr’s interpretation of the atom (1913)?

Answer 16

He modified Rutherford’s model of the atom by stating electrons move around the nucleus in orbits of fixed sizes and energies. Electron energy in this model was quantised.

Question 17

What was correct about Niels Bohr’s interpretation of the atom?

Answer 17

Proposed stable electron orbits; explained the emission spectra of some elements.

Question 18

What was incorrect about Niels Bohr’s interpretation of the atom?

Answer 18

Moving electrons should emit energy and collapse into the nucleus; the model did not work well for heavier atoms.

Question 19

What experiment led to the new model of the atom by Ernest Rutherford?

Answer 19

The alpha particles scattering experiment.

Question 20

What is the alpha particles scattering experiment?

Answer 20

Ernest Rutherford fired alpha particles at a thin gold foil and unexpectedly observed some particles were deflected at large angles, even bouncing back created as flashes on the fluorescent screen, leading to the discovery of the atomic nucleus.

Question 21

What is filtration?

Answer 21

It is used to separate an insoluble solid from a liquid or solution by passing the mixture through filter paper, allowing the liquid (the filtrate) to pass through while retaining the solid as residue.

Question 22

What is evaporation?

Answer 22

It is used to isolate a dissolved solid (solute) from a liquid (solvent) by heating the solution, allowing the solvent to evaporate, and leaving the solid residue behind.

Question 23

What is distillation?

Answer 23

It uses evaporation and condensation to separate a liquid from a solution or to separate different liquids based on their boiling points.

Question 24

What is chromatography?

Answer 24

It is used to separate different substances dissolved in a liquid with different solubilities.

Question 25

What is the relative size of an atom?

Answer 25

They have a radius of about 0.1nm or 1×10¹⁰ metres.

Question 26

What are isotopes?

Answer 26

Atoms of the same element with the same number of protons but different numbers of neutrons, resulting in different atomic masses.

Question 27

What are the three subatomic particles?

Answer 27

A proton, a neutron and an electron.

Question 28

What are the vertical columns of a periodic table called?

Answer 28

Groups.

Question 29

Why are atoms in the same group similar?

Answer 29

They have the same number of electrons in their outer shell/orbit.

Question 30

Who is responsible for the modern periodic table?

Answer 30

Dimitri Mendeleev.

Question 31

How did the periodic table develop?

Answer 31

Before the discovery of protons, neutrons and electrons, scientists attempted to classify the elements by arranging them in order of atomic weights, not mass. Mendeleev overcame some of the problems by leaving gaps for elements he thought had not been discovered and, in some places, changed the order based on atomic weights. Elements with properties predicted by Mendeleev were discovered and filled the gaps. Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct.

Question 32

What is an ion?

Answer 32

An atom with a positive or negative charge due to a gain or loss of (an) electron(s).

Question 33

What ion do metal atoms form?

Answer 33

Positively charged ions.

Question 34

What are Group 0 elements?

Answer 34

Noble gases; they are unreactive and do not easily form molecules.

Question 35

How do atoms become ions?

Answer 35

By gaining or losing electrons in ionic bonding.

Question 36

What is the trend shown by Group 1 elements?

Answer 36

Reactivity increases down the group.

Question 37

Why do alkali metals (Group 1 elements) become more reactive as you go down the group?

Answer 37

Outer electrons are further from the nucleus, meaning there is a weaker electrostatic force, meaning it can be lost more easily.

Question 38

How do Group 1 elements react with oxygen and water?

Answer 38

They oxidised quickly are are very malleable. They explode in contact with water.

Question 39

How does Lithium react with water?

Answer 39

It floats with gentle fizzing and hydrogen gas release. It gradually dissolves to give a colourless solution (LiOH). The final solution has pH12-14.

Question 40

How does Sodium react with water?

Answer 40

It floats with igorous fizzing and hydrogen gas release. It melts and rapidly dissolves to give a colourless solution (NaOH). The final solution has pH14.

Question 41

How does Potassium react with water?

Answer 41

It floats with very vigorous fizzing and hydrogen gas release, which bursts into a lilac flame, and it very rapidly dissolves to give a colourless solution (KOH). The final solution has pH14.

Question 42

How does Rubidium react with water?

Answer 42

It sinks and explosively releases hydrogen gas and instantaneously dissolves to give a colourless solution (RbOH). The final solution has pH14.

Question 43

What is the trend shown in group 7 elements?

Answer 43

The reactivity decreases down the group.

Question 44

Why do halogens (Group 7 elements) become less reactive the further down the group?

Answer 44

The outer electrons are further from the nucleus, meaning there are weaker electrostatic forces between the nucleus and the incoming electron, which is gained less readily.

Question 45

What is displacement in a reaction?

Answer 45

When a more reactive element takes the place of a less reactive element in a compound.