1. Atomic Structure and the Periodic Table

Question 1

What are atoms?

Answer 1

All substances are made of atoms, which are extremely tiny.

Question 2

What is the radius of an atom?

Answer 2

About 0.1 nanometres (1 × 10^-10 m).

Question 3

What is a nanometre (nm)?

Answer 3

A nanometre is one billionth of a metre (1 × 10^-9 m).

Question 4

Where is the nucleus located in an atom?

Answer 4

In the middle of the atom.

Question 5

What does the nucleus contain?

Answer 5

Protons and neutrons.

Question 6

What is the radius of the nucleus?

Answer 6

Around 1 × 10^-14 m.

Question 7

What charge does the nucleus have?

Answer 7

Positive charge due to protons.

Question 8

Where is most of the mass of an atom concentrated?

Answer 8

In the nucleus.

Question 9

How do electrons move in an atom?

Answer 9

They move around the nucleus in electron shells.

Question 10

What is the charge of electrons?

Answer 10

Negatively charged.

Question 11

What determines the size of the atom?

Answer 11

The volume of the electrons’ orbits.

Question 12

What is the relative mass of protons?

Answer 12

1

Question 13

What is the relative charge of neutrons?

Answer 13

0 (neutral).

Question 14

What is the relative charge of electrons?

Answer 14

-1.

Question 15

What is true about the number of protons and electrons in an atom?

Answer 15

They are equal, making the atom neutral.

Question 16

What is an ion?

Answer 16

An atom or group of atoms that has lost or gained electrons.

Question 17

What does the atomic number represent?

Answer 17

The number of protons in an atom.

Question 18

What does the mass number represent?

Answer 18

The total number of protons and neutrons in an atom.

Question 19

How do you calculate the number of neutrons in an atom?

Answer 19

Subtract the atomic number from the mass number.

Question 20

What is the relative mass of an electron?

Answer 20

Approximately 1/1840 or 1/2000.

Question 21

What is an element?

Answer 21

A substance made up of atoms that all have the same number of protons in their nucleus.

Question 22

What determines the type of atom?

Answer 22

The number of protons in the nucleus.

Question 23

What is the atomic number?

Answer 23

The number of protons in an atom’s nucleus.

Question 24

What element has one proton in its nucleus?

Answer 24

Hydrogen.

Question 25

What element has two protons in its nucleus?

Answer 25

Helium.

Question 26

What do we call a substance that only contains atoms with the same number of protons?

Answer 26

An element.

Question 27

How many different elements are there approximately?

Answer 27

About 100.

Question 28

What is the representation of atoms of each element?

Answer 28

A one or two letter symbol.

Question 29

What does the symbol 'C' represent?

Answer 29

Carbon.

Question 30

What does the symbol 'O' represent?

Answer 30

Oxygen.

Question 31

What does the symbol 'Mg' represent?

Answer 31

Magnesium.

Question 32

What does the symbol 'Na' represent?

Answer 32

Sodium.

Question 33

What does the symbol 'Fe' represent?

Answer 33

Iron.

Question 34

What does the symbol 'Pb' represent?

Answer 34

Lead.

Question 35

Why do some element symbols seem odd?

Answer 35

They come from the Latin names of the elements.

Question 36

Fill in the blank: An element consists of only one type of _______.

Answer 36

Atom.

Question 37

What are isotopes?

Answer 37

Different forms of the same element, which have the same number of protons but a different number of neutrons.

Question 38

How do isotopes differ from each other?

Answer 38

Isotopes differ in the number of neutrons and, consequently, in their mass numbers.

Question 39

What is the relationship between atomic number and mass number for isotopes?

Answer 39

Isotopes have the same atomic number but different mass numbers.

Question 40

Give an example of a pair of isotopes.

Answer 40

Carbon-12 and Carbon-13.

Question 41

What are the neutron counts for Carbon-12 and Carbon-13?

Answer 41

Carbon-12 has 6 neutrons, while Carbon-13 has 7 neutrons.

Question 42

What is relative atomic mass?

Answer 42

An average mass taking into account the different masses and abundances of all the isotopes that make up the element.

Question 43

Why is relative atomic mass used instead of mass number?

Answer 43

Because many elements can exist as a number of different isotopes.

Question 44

How do you calculate the relative atomic mass of an element?

Answer 44

relative atomic mass (A) = sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes.

Question 45

Fill in the blank: Isotopes of an element have different _______.

Answer 45

mass numbers.

Question 46

Define a compound.

Answer 46

Substances formed from two or more elements in fixed proportions held together by chemical bonds.

Question 47

What is usually required to separate the original elements of a compound?

Answer 47

A chemical reaction.

Question 48

What typically occurs during a chemical reaction?

Answer 48

At least one new substance is made and a change in energy is usually measurable.

Question 49

How do the properties of a compound compare to the properties of the original elements?

Answer 49

They are usually totally different.

Question 50

What did John Dalton describe atoms as at the start of the 19th century?

Answer 50

Solid spheres ## Footnote Dalton proposed that different spheres made up the different elements.

Question 51

What significant discovery did J.J. Thomson make in 1897 about atoms?

Answer 51

Atoms contain smaller, negatively charged particles called electrons ## Footnote Thomson's experiments revealed that atoms were not solid spheres.

Question 52

What is the 'plum pudding model'?

Answer 52

An atomic model showing the atom as a ball of positive charge with electrons stuck in it ## Footnote This model replaced the solid sphere idea of atomic structure.

Question 53

Who conducted the alpha particle scattering experiments in 1909?

Answer 53

Ernest Rutherford and Ernest Marsden ## Footnote Their experiments provided evidence against the plum pudding model.

Question 54

What was the expected outcome of Rutherford's alpha particle scattering experiments based on the plum pudding model?

Answer 54

Particles would pass straight through or be slightly deflected ## Footnote The positive charge was thought to be spread out through the atom.

Question 55

What unexpected results were observed in Rutherford's alpha particle scattering experiments?

Answer 55

Some particles were deflected more than expected, and a small number were deflected backwards ## Footnote This indicated that the plum pudding model was incorrect.

Question 56

What model did Rutherford propose after his experiments?

Answer 56

The nuclear model of the atom ## Footnote This model features a tiny, positively charged nucleus at the center.

Question 57

In the nuclear model, what surrounds the nucleus?

Answer 57

A cloud of negative electrons ## Footnote Most of the atom is considered empty space.

Question 58

Fill in the blank: In the nuclear model, the nucleus contains most of the _______.

Answer 58

Mass ## Footnote The nucleus is a concentrated positive charge.

Question 59

True or False: Most alpha particles passed through the gold sheet in Rutherford's experiments.

Answer 59

True ## Footnote Most particles passed through empty space with few being deflected.