C2 Atoms, elements and compounds

What is an element?

a substance made from only one type of atom, they are pure substances that can’t be broken down any further

What is an atom?

the smallest unit of matter

What is a molecule?

group of two or more atoms bonded together. the atoms can be the same or different

What is a compound?

a substance made from two or more elements chemically bonded together

What is a mixture?

a combination of two or more substances that aren’t chemically bonded together

Draw the structure of an atom

Describe the structure of an atom

atoms contain a positively charged nucleus made of positively charged protons and no charge neutrons surrounded by negatively charged electrons arranged in shells

Fill in this table

Which of these is the atomic number and which is the mass number?

Smaller number=atomic number

Bigger number=mass number

What is the proton number/atomic number?

the number of protons in the nucleus of an atom

What is equal to the number of protons?

number of protons=number of electrons

What is the mass number/nucleon number?

the total number of protons and neutrons in the nucleus of an atom

How to find number of protons, electrons and neutrons?

protons= atomic number

electrons=number of protons (atomic number)

neutrons= mass number - atomic number

What is the electron configuration based on?

atomic number

Electron configuration rule

1st shell=2

2nd shell=8

3rd shell=8

Find the electron configuration for the first 20 elements

Hydrogen (H): 1

Helium (He): 2

Lithium (Li): 2, 1

Beryllium (Be): 2, 2

Boron (B): 2, 3

Carbon (C): 2, 4

Nitrogen (N): 2, 5

Oxygen (O): 2, 6

Fluorine (F): 2, 7

Neon (Ne): 2, 8

Sodium (Na): 2, 8, 1

Magnesium (Mg): 2, 8, 2

Aluminum (Al): 2, 8, 3

Silicon (Si): 2, 8, 4

Phosphorus (P): 2, 8, 5

Sulfur (S): 2, 8, 6

Chlorine (Cl): 2, 8, 7

Argon (Ar): 2, 8, 8

Potassium (K): 2, 8, 8, 1

Calcium (Ca): 2, 8, 8, 2

In a periodic table, what is each row/going across called?

a period

In a periodic table, what is each column/going down called?

a group

What is group VIII (8) called and what do they have?

noble gases have a full outer shell

What does the group number in Groups I to VII (7) tells you?

the number of electrons in the outer-shell

What does the period number tell you?

the number of occupied electron shells

What is an isotope?

atoms of the same element that have the same number of electrons and protons but different number of neutrons

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

because they have the same number of electrons in the outer shell and therefore the same electronic configuration

Interpret this symbol

X=element symbol

A=mass number

Z=atomic number

What is the relative atomic mass?

the average mass of atoms of a chemical element compared to one twelfth of a mass of carbon-12

How to calculate the relative atomic mass?

What is an ion?

an atom or molecule with an electrical charge due to loss or gain of an electron

What is the charge of an atom to start with?

neutral because there are the same amount of positive protons and negative electrons

What is an cation?

positive ions formed from the loss of an electron from a metal

How is a cation formed?

A metal always loses electrons to get a full outer shell, this means it ends up with more positive protons than negative electrons, the overall charge of the particle is now positive

What is an anion?

negative ions formed from the gain of an electron to a non-metal

How is an anion formed?

A non-metal always gains electrons to get a full outer shell, this means it ends up with more negative electrons than positive protons, the overall charge of the particle is now negative

What is an ionic bond?

a strong electrostatic attraction between oppositely charged ions

-electrostatic attraction is the bond created between atoms/molecules of opposite charge

What do ionic bonds occur between?

a metal and non-metal/cation and anion

Draw a dot-and-cross diagram for MgO

Draw a dot-and-cross diagram for Na₂O

Draw a dot-and-cross diagram for NaF

Draw a dot-and-cross diagram for Al₂O₃

What are the properties of ionic compounds?

-high melting points and boiling points

-good electrical conductivity when aqueous or molten and poor when solid

-generally soluble in water

Explain why ionic compounds have high melting points and boiling points

the ionic bonds have very strong electrostatic attraction so more energy is needed to overcome them and change state

Explain why ionic compounds are good electrical conductivity when aqueous or molten and poor when solid

-good electrical conductivity when aqueous or molten because the ions are free to move around and carry charge

-poor conductor when solid because the ions are fixed in position and can’t move from one place to another

What is a giant lattice structure of ionic compound?

a regular arrangement of alternating positive and negative ion

What is the overall charge of a giant lattice structure of ionic compound?

neutral

Draw a giant lattice structure for sodium chloride

What is the overall charge for a giant lattice structure for sodium chloride?

neutral

What is a covalent bonding?

the sharing of electrons between two non-metals formed when a pair of electrons is shared between two atoms leading to noble gas electronic configurations

What is a covalent bond?

the electrostatic attraction between positive nuclei and negative shared electrons

Draw a dot-and-cross diagram for H₂

Draw a dot-and-cross diagram for Cl₂

Draw a dot-and-cross diagram for H₂O

Draw a dot-and-cross diagram for CH₄

Draw a dot-and-cross diagram for NH₃

Draw a dot-and-cross diagram for HCl

Draw a dot-and-cross diagram for CH₃OH

Draw a dot-and-cross diagram for C₂H₄

Draw a dot-and-cross diagram for O₂

Draw a dot-and-cross diagram for CO₂

raw a dot-and-cross diagram for N₂

What are the properties of simple molecular compounds (covalent)?

-low melting points and boiling points

-poor electrical conductivity

Explain why simple molecular compounds (covalent) have low melting points and boiling points

the covalent bonds within the molecules are very strong and hard to break but the forces between the molecules called the intermolecular forces are weak and need little energy to break and change state

Explain why simple molecular compounds (covalent) are bad electrical conductors

there are no free ions to carry charge

What is a giant covalent structure?

a substance where large number of atoms are held together by covalent bonds forming a strong lattice structure that extends itself in all directions

What is the giant covalent structure for diamond like?

Each carbon atom is covalently bonded to 4 other carbon atoms

-its structure is a tetrahedral 3D shape

Draw the giant covalent structure for diamond

Properties of diamonds and why

-hard due to many strong covalent bonds

-high melting point and boiling point

-doesn’t conduct electricity

What are diamonds used in? + why

cutting tools because its very hard due to rigid structure held together by strong covalent bonds

What is the giant covalent structure for graphite like?

Each carbon atom is covalently bonded to 3 other carbon atoms

-its structure consists of layers of hexagonal rings with no covalent bonds between the layers

Draw the giant covalent structure for graphite

Properties of graphite and why

-Soft because the layers are connected by weak intermolecular forces so they can slide over each other

-high melting and boiling points

-can conduct electricity as one electron from each carbon atom is delocalised and can carry charge

What is graphite used in? + why

lubricant-slippery as the layers can slide over each other due to weak intermolecular forces

conductor-can conduct electricity due to delocalised electron

What is the giant covalent structure for silicon(IV) oxide (silicon dioxide), SiO₂ like?

-each silicon atom is covalently bonded to 4 oxygen atoms

-each oxygen atom is covalently bonded to 2 silicon atoms

What are the similarity between diamonds and silicon(IV) oxide?

-high melting points and boiling points- both have strong covalent bonds which require a lot of energy to break

-don’t conduct electricity- both don’t have free electrons or ions to move and carry charge

-hard and rigid-both have atoms bonded in a tetrahedral arrangement

What is metallic bond?

the electrostatic attraction between the positive ions in a giant metallic lattice and a ‘sea’ of delocalised electrons

What is the process of metallic bonding?

the delocalisation of outer electrons from the metal atoms

What does metallic bonding look like (diagram)?

Why can metals conduct electricity?

the delocalised electrons can move around structure and carry charge

Why are metals malleable and ductile?

the positive ions are arranged in layers with a regular arrangement so the layers are able to slide over each other

Why do metals have high melting and boiling points?

strong electrostatic attraction between negatively charged electrons and positive metal ions so require a lot of energy to overcome the strong metallic bond