c2

c2 aqa

HideShow resource information
  • Created by: rakhi
  • Created on: 01-01-11 16:06
Preview of c2

First 284 words of the document:

Atomic structure and Bonding:
Atomic Structures:
Atoms consist of electrons surrounding a nucleus that contains protons and neutrons. Neutrons
are neutral, but protons and electrons are electrically charged. Protons have a positive charge and
electrons have a negative charge. The number of protons in an atom is called its atomic number. In
the periodic table atoms are arranged in atomic number order. Electrons are arranged in energy
levels or shells, and different energy levels can hold different numbers of electrons. The electronic
structure of an atom is a description of how the electrons are arranged, which can be shown in a
diagram or by numbers. There is a link between the position of an element in the periodic table and
its electronic structure.
The structure of an atom:
Atoms are made from smaller subatomic particles. At the centre of
an atom is a nucleus containing protons and neutrons.
Electrons are arranged around the nucleus in energy levels or shells.
Both protons and electrons have an electrical charge. Both have the
same size of electrical charge, but the proton is positive and the
electron negative. The neutron is neutral.
The electrical charge of particles:
The total number of electrons in an atom is always the same as the number of protons in the
nucleus. This means atoms have no overall electrical charge.
The number of protons in an atom is called its atomic number, also called the proton number.
Atoms are arranged in the periodic table in order of increasing atomic number.
Particle Relative charge
Proton +1
Neutron 0
Electron 1

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Energy levels and shells:
Electrons are arranged in different shells around the nucleus. The innermost shell, or lowest
energy level, is filled first. Each succeeding shell can only hold a certain number of electrons before
it becomes full. The innermost shell can hold a maximum of two electrons, the second shell a
maximum of eight, and so on.
Energy level or shell Maximum number of electrons
First 2
Second 8
Third 8
Fourth 18
A lithium atom, for example, has three electrons.…read more

Page 3

Preview of page 3

Here's a taster:

Electronic structure:
The electronic structure of an atom is a description of how the electrons are arranged. The first 20
elements in the periodic table run from hydrogen to calcium. Their electronic structures can be
shown either as diagrams or numbers. The number of electrons in the highest occupied energy
level of each atom is the same as the element's group number.
Element Numeric Electrons Periodic table group
format
Li 2,1 Lithium atoms have three electrons.…read more

Page 4

Preview of page 4

Here's a taster:

Ca 2,8,8,2 Calcium atoms have 20 electrons. Group 2
Two of these fit into the first energy
level, eight into the second energy
level, another eight into the third
energy level. The last two fit into the
fourth energy level.
Electronic structure and the periodic table:
There is a link between an atom's electronic structure and its position in the periodic table.
You can work out an atom's electronic structure from its place in the periodic table.…read more

Page 5

Preview of page 5

Here's a taster:

Ionic Bonding:
Ions are electrically charged particles formed when atoms lose or gain electrons. They have the
same electronic structures as noble gases. Metal atoms form positive ions, while nonmetal atoms
form negative ions. The strong electrostatic forces of attraction between oppositely charged ions
are called ionic bonds. Ionic compounds have high melting and boiling points.
How ions form:
Ions are electrically charged particles formed when atoms lose or gain electrons.…read more

Page 6

Preview of page 6

Here's a taster:

Metal ions:
Lithium is in Group 1. It has one electron in its highest energy level. When this electron is lost, a
lithium ion Li+ is formed.
Sodium is also in Group 1. It has one electron in its highest energy level. When this electron is
lost, a sodium ion Na+ is formed.
A sodium ion has the same electronic structure as a neon atom (Ne).A sodium ion is not a neon
atom.…read more

Page 7

Preview of page 7

Here's a taster:

Magnesium is in Group 2. It has two electrons in its highest energy level. When these electrons
are lost, a magnesium ion Mg2+ is formed. A magnesium ion has the same electronic structure as
a neon atom (Ne).
Calcium is also in Group 2. It has two electrons in its highest energy level. When these electrons
are lost, a calcium ion Ca2+ is formed. A calcium ion has the same electronic structure as an argon
atom (Ar).
Nonmetal ions:
Fluorine is in Group 7.…read more

Page 8

Preview of page 8

Here's a taster:

Chlorine is in Group 7. It has seven electrons in its highest energy level. It gains an electron from
another atom in reactions, forming a chloride ion, Cl.
Oxygen is in Group 6. It has six electrons in its highest energy level. It gains two electrons from one
or two other atoms in reactions, forming an oxide ion, O2.…read more

Page 9

Preview of page 9

Here's a taster:

Ionic compounds and ionic bonding:
When metals react with nonmetals, electrons are transferred from the metal atoms to the
nonmetal atoms, forming ions. The resulting compound is called an ionic compound.
Consider reactions between metals and nonmetals, for example,
sodium + chlorine sodium chloride
magnesium + oxygen magnesium oxide
calcium + chlorine calcium chloride
In each of these reactions, the metal atoms give electrons to the nonmetal atoms. The metal
atoms become positive ions and the nonmetal atoms become negative ions.…read more

Page 10

Preview of page 10

Here's a taster:

Dot & Cross diagrams:
Sodium ions have the formula Na+, while chloride ions have the formula Cl. You need to show one
sodium ion and one chloride ion.
Magnesium ions have the formula Mg2+, while oxide ions have the formula O2. You need to show
one magnesium ion and one oxide ion.
Calcium ions have the formula Ca2+. Chloride ions have the formula Cl. Two chloride ions are
needed to balance the charge on a calcium ion.…read more

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all resources »