Atomic Structure

What are the three subatomic particles?

Protons neutrons and electrons

What is the relative charge of a proton?

+1

What is the relative charge of a neutron?

0

What is the relative charge of an electron?

-1

What is the relative mass of a proton?

1

What is the relative mass of a neutron?

1

What is the relative mass of an electron?

Very small approximately 1/1840 of a proton

Where are protons found?

In the nucleus

Where are neutrons found?

In the nucleus

Where are electrons found?

In shells around the nucleus

What is the atomic number of an element?

The number of protons in its nucleus

What is the mass number of an atom?

The total number of protons and neutrons

How do you calculate the number of neutrons?

Mass number minus atomic number

Why does an atom have no overall charge?

It has equal numbers of protons and electrons

What is an isotope?

Atoms of the same element with the same number of protons but different numbers of neutrons

Why do isotopes of the same element have the same chemical properties?

They have the same number and arrangement of electrons

Why can isotopes have different physical properties?

They have different masses because they contain different numbers of neutrons

What does the atomic number tell you about an element?

Its number of protons and therefore its identity

What happens to an atom when it loses electrons?

It becomes a positive ion

What happens to an atom when it gains electrons?

It becomes a negative ion

What is an ion?

A charged particle formed when an atom or group of atoms gains or loses electrons

What is the electron arrangement of sodium?

2,8,1

What is the electron arrangement of magnesium?

2,8,2

What is the electron arrangement of chlorine?

2,8,7

What is the electron arrangement of calcium?

2,8,8,2

Why are noble gases unreactive?

They have a full outer electron shell

What is the maximum number of electrons in the first shell?

2

How many electrons can the second shell hold at GCSE level?

8

How many electrons can the third shell hold at GCSE level?

8 for the first 20 elements

What determines the chemical properties of an element?

The arrangement of its electrons particularly the outer-shell electrons

What is the charge of an electron?

-1

What is the charge of an ion with 11 protons and 10 electrons?

+1

What is the charge of an ion with 17 protons and 18 electrons?

-1

An atom has atomic number 13 and mass number 27. How many neutrons does it have?

14

An atom has 12 protons and 12 neutrons. What is its mass number?

24

An atom has 16 protons and 18 electrons. What is its charge?

-2

Why do elements in the same group have similar chemical properties?

They have the same number of electrons in their outer shell

What is a group in the periodic table?

A vertical column

What is a period in the periodic table?

A horizontal row

What does the period number tell you?

The number of occupied electron shells

What does the group number tell you for Groups 1 to 7?

The number of electrons in the outer shell

Where are metals found in the periodic table?

Mostly on the left and centre

Where are non-metals found in the periodic table?

Mostly on the right

What is Group 1 called?

The alkali metals

What is Group 7 called?

The halogens

What is Group 0 called?

The noble gases

What is the trend in reactivity down Group 1?

Reactivity increases

Why does Group 1 reactivity increase down the group?

The outer electron is further from the nucleus and more shielded so it is easier to lose

What happens to the melting and boiling points of Group 1 metals down the group?

They generally decrease

What happens when a Group 1 metal reacts with water?

It forms a metal hydroxide and hydrogen

What is the general equation for a Group 1 metal reacting with water?

Metal + water → metal hydroxide + hydrogen

What is the trend in reactivity down Group 7?

Reactivity decreases

Why does Group 7 reactivity decrease down the group?

The incoming electron is further from the nucleus and more shielded so attraction is weaker

What type of particles do Group 7 elements form when they react?

Negative ions

What is the general reaction when a halogen reacts with a metal?

Halogen + metal → metal halide

What is a displacement reaction involving halogens?

A more reactive halogen displaces a less reactive halogen from its compound

How can you compare the reactivity of halogens experimentally?

Add different halogens to solutions containing halide ions and observe whether displacement occurs

What is Group 0's key characteristic?

They have full outer electron shells

What happens to boiling points of noble gases down Group 0?

They generally increase

Why do noble gases have low boiling points?

They are monatomic and only have weak intermolecular forces between their atoms

What was Dalton's model of the atom?

Atoms were tiny solid spheres that could not be divided

What did Thomson discover?

The electron

What was Thomson's atomic model?

A positive sphere with electrons embedded in it

What did Rutherford's alpha scattering experiment show?

The atom has a tiny dense positive nucleus and is mostly empty space

Why was Rutherford's discovery significant?

It disproved the plum pudding model

What did Bohr propose about electrons?

Electrons orbit the nucleus at fixed distances in shells

What did Chadwick discover?

The neutron

Why did the atomic model change over time?

New experimental evidence showed that previous models were incomplete or incorrect

What did the alpha scattering experiment involve?

Firing alpha particles at a thin sheet of gold and observing their deflections

Why did most alpha particles pass straight through the gold foil?

Atoms are mostly empty space

Why were some alpha particles deflected strongly?

They passed close to or directly towards the positively charged dense nucleus

Why did a very small number of alpha particles bounce backwards?

They hit or came extremely close to the dense nucleus

What is relative atomic mass?

The weighted mean mass of an atom of an element compared with one twelfth of the mass of a carbon-12 atom

Why is relative atomic mass often not a whole number?

It is a weighted mean of the masses of the element's naturally occurring isotopes

How do you calculate relative atomic mass from isotope data?

Multiply each isotope mass by its fractional abundance then add the values

What is the difference between atomic number and mass number?

Atomic number is protons only whereas mass number is protons plus neutrons

Why does changing the number of protons create a different element?

The number of protons determines the element's identity

Why does changing the number of electrons not create a new element?

The element's identity is determined by proton number

Why does changing the number of neutrons not create a new element?

Isotopes have different neutron numbers but remain the same element

What happens to the electron arrangement when a positive ion forms?

Electrons are removed from the outer shell

What happens to the electron arrangement when a negative ion forms?

Electrons are added to the outer shell

Why do atoms form ions?

To obtain a more stable electron arrangement often with a full outer shell

How is the modern periodic table arranged?

Elements are arranged in order of increasing atomic number

Why can elements in the same group have similar reactions?

They have the same number of outer-shell electrons

Why does atomic radius generally increase down a group?

Additional electron shells are added

What is shielding in an atom?

Inner electron shells reduce the attraction between the nucleus and outer electrons

What happens to nuclear charge across a period?

It increases because the number of protons increases

Why does atomic radius generally decrease across a period?

Nuclear charge increases while electrons are added to the same main shell so attraction becomes stronger

What is the relationship between group number and outer electrons for Group 1–7 elements?

The group number corresponds to the number of outer-shell electrons

What is the relationship between period number and electron shells?

The period number equals the number of occupied electron shells