Chemy

What is the Periodic Table?

A table that organises elements by atomic number and repeating chemical properties.

What is atomic number?

The number of protons in an atom's nucleus.

What is mass number?

The total number of protons and neutrons in an atom.

What is a group?

A vertical column on the Periodic Table.

What is a period?

A horizontal row on the Periodic Table.

What do elements in the same group generally have in common?

They have similar chemical properties and, for the main groups, the same number of valence electrons.

What are valence electrons?

Electrons in the outermost occupied electron shell.

Why are valence electrons important?

They determine many of an element's chemical properties and how it bonds.

What are Group 1 elements called?

Alkali metals.

How many valence electrons do Group 1 elements have?

One.

How does Group 1 reactivity change down the group?

It generally increases.

What are Group 2 elements called?

Alkaline earth metals.

How many valence electrons do Group 2 elements have?

Two.

What are Group 17 elements called?

Halogens.

How many valence electrons do Group 17 elements have?

Seven.

How does Group 17 reactivity generally change down the group?

It generally decreases.

What are Group 18 elements called?

Noble gases.

Why are noble gases very unreactive?

They have full outer electron shells.

What are metals?

Elements generally found on the left and centre of the Periodic Table that are usually good conductors, malleable and ductile.

What are non-metals?

Elements generally found on the right side of the Periodic Table that are usually poor conductors.

What are metalloids?

Elements with properties between those of metals and non-metals.

What is an atom?

The smallest unit of an element that retains the chemical properties of that element.

What is the nucleus?

The dense central region of an atom containing protons and neutrons.

What is a proton?

A positively charged subatomic particle in the nucleus.

What is a neutron?

A neutral subatomic particle in the nucleus.

What is an electron?

A negatively charged subatomic particle found outside the nucleus.

What is the charge of a proton?

+1.

What is the charge of a neutron?

0.

What is the charge of an electron?

-1.

What is an ion?

A charged particle formed when an atom gains or loses electrons.

What is a cation?

A positively charged ion formed when an atom loses electrons.

What is an anion?

A negatively charged ion formed when an atom gains electrons.

What is electron configuration?

The arrangement of electrons in shells or energy levels.

What is the electron configuration of sodium?

2,8,1.

What is the electron configuration of chlorine?

2,8,7.

What is the electron configuration of calcium?

2,8,8,2.

Why do atoms form ions?

They can gain or lose electrons to obtain a more stable outer electron arrangement.

What is ionic bonding?

The electrostatic attraction between oppositely charged ions formed after electrons are transferred.

What types of elements usually form ionic compounds?

A metal and a non-metal.

What happens to a metal in ionic bonding?

It loses one or more electrons and becomes a positive ion.

What happens to a non-metal in ionic bonding?

It gains one or more electrons and becomes a negative ion.

Why must an ionic compound have an overall charge of zero?

The positive and negative charges must balance.

How are ionic compounds named?

Name the metal/cation first, followed by the non-metal with its ending changed to -ide.

What is NaCl called?

Sodium chloride.

What is MgO called?

Magnesium oxide.

What is CaCl2 called?

Calcium chloride.

What is Al2O3 called?

Aluminium oxide.

How do you write the formula of an ionic compound?

Choose subscripts so that the total positive charge equals the total negative charge.

What is the formula for magnesium chloride?

MgCl2.

Why is magnesium chloride MgCl2?

Mg2+ needs two Cl- ions to give an overall charge of zero.

What is the formula for aluminium oxide?

Al2O3.

What are typical physical properties of ionic compounds?

They are usually hard, brittle, crystalline and have high melting and boiling points.

Do solid ionic compounds conduct electricity?

No, because their ions are fixed in position.

Do molten ionic compounds conduct electricity?

Yes, because their ions are free to move.

Do ionic compounds conduct when dissolved in water?

Many do, because their ions are free to move.

What is covalent bonding?

A bond formed when non-metal atoms share electrons.

What elements usually form covalent compounds?

Non-metals.

What is a single covalent bond?

A bond where two atoms share one pair of electrons.

What is a double covalent bond?

A bond where two atoms share two pairs of electrons.

What is a triple covalent bond?

A bond where two atoms share three pairs of electrons.

Why do atoms form covalent bonds?

They share electrons to achieve a more stable outer electron arrangement.

What is a covalent compound?

A compound formed from non-metal atoms joined by covalent bonds.

What are typical properties of simple molecular covalent compounds?

Many have low melting and boiling points and do not conduct electricity.

Why do simple molecular covalent compounds often have low melting points?

The forces between separate molecules are relatively weak.

Why don't simple covalent compounds usually conduct electricity?

They generally lack freely moving charged particles.

What is a diatomic molecule?

A molecule containing two atoms of the same element.

What are the seven diatomic elements?

Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine.

What are the formulas of the seven diatomic elements?

H2, N2, O2, F2, Cl2, Br2 and I2.

What is the diatomic molecule of oxygen?

O2.

What is the diatomic molecule of chlorine?

Cl2.

What is metallic bonding?

The attraction between positive metal ions and a sea of delocalised electrons.

What are delocalised electrons?

Electrons that are free to move throughout a metallic structure.

Why do metals conduct electricity?

Their delocalised electrons can move through the metal and carry electrical charge.

Why do metals conduct heat?

Delocalised electrons can transfer energy through the metal.

What does malleable mean?

Can be hammered or pressed into sheets without breaking.

What does ductile mean?

Can be drawn into wires without breaking.

What are typical physical properties of metals?

They are generally shiny, strong, malleable, ductile and good conductors of heat and electricity.

What is a hydrocarbon?

A compound containing only carbon and hydrogen.

What is an alkane?

A hydrocarbon containing only single carbon-carbon bonds.

What is the general formula for alkanes?

CnH2n+2.

What is the first alkane?

Methane, CH4.

What is the second alkane?

Ethane, C2H6.

What is the third alkane?

Propane, C3H8.

What is the fourth alkane?

Butane, C4H10.

What is the fifth alkane?

Pentane, C5H12.

What is the sixth alkane?

Hexane, C6H14.

What is the seventh alkane?

Heptane, C7H16.

What is the eighth alkane?

Octane, C8H18.

What are the first eight alkane prefixes?

Meth-, eth-, prop-, but-, pent-, hex-, hept- and oct-.

What ending do alkane names have?

-ane.

What is a Lewis-dot diagram?

A diagram showing an atom's valence electrons as dots around its chemical symbol.

What is the purpose of a Lewis-dot diagram?

To show valence electrons and help predict how atoms will bond.

How many valence electrons does carbon have?

Four.

How many valence electrons does nitrogen have?

Five.

How many valence electrons does oxygen have?

Six.

How many valence electrons does chlorine have?

Seven.

How many valence electrons does sodium have?

One.

What is the octet rule?

Atoms tend to gain, lose or share electrons to achieve a stable outer shell, often containing eight electrons.

What does a Lewis diagram for ionic bonding show?

Electrons being transferred and the resulting ions.

What does a Lewis diagram for covalent bonding show?

Shared pairs of electrons between atoms.