Year 10 Chemistry

• Atomic Structure (x2)

• The Periodic Table

• Chemical Symbols

• Ions

• Oxidation and Reduction

• Rates of Reaction

• Rates of Reaction EQUATION

• Affecting Factors

• Gases In the Atmosphere

• Evolution of the Atmosphere

• Changes in the Atmosphere

What are atoms made of?

Every atom is made of a nucleus consisting of protons and neutrons. The nucleus is surrounded by electrons.

What are the charges of protons, electrons, nuetrons and the atom nucleus?

Protons and electrons are oppositely charged. Neutrons have no charge. This means the nucleus of an atom is always positively charged. It is very small compared to the size of the atom.

What is the overall charge of an atom and why?

An atom has a neutral overall charge because it has the same number of electrons as protons.

What are the masses of protons, nuetrons and electrons?

Protons and neutrons have the same mass. Electrons have such a small mass that this can usually be taken as zero.

What is the atomic number?

The atomic number (also called the proton number) is the number of protons in an atom. All the atoms of the same element have the same number of protons – a number that is unique to that element.

What is the mass number?

The mass number (also called the nucleon number) is the total number of protons and neutrons in an atom.

The atomic number (also called the proton number) is the number of protons it contains

The mass number of an atom is the total number of protons and neutrons it contains.

How are the elements arranged in the Periodic Table?

The elements are arranged in the Periodic Table in ascending order of atomic number so it's easy to find the name or symbol for an atom if you know the atomic number.

Most elements exist in a number of different forms or varieties called isotopes.

What are isotopes?

Isotopes have the same number of protons but different numbers of neutrons, which gives them a different total mass. That means isotopes of an element have the same atomic number but different mass numbers.

The full chemical symbol for an element shows its mass number at the top, and atomic number at the bottom. Here is the full symbol for carbon.

 The chemical symbol for carbon

It tells us that a carbon atom has six protons. It will also have six electrons, because the number of protons and electrons in an atom is the same.

The symbol also tells us that the total number of protons and neutrons in a carbon atom is 12. Note that you can work out the number of neutrons from the mass number and atomic number. In this example, it is 12 - 6 = 6 neutrons.

What are ions?

Ions are electrically charged particles formed when atoms lose or gain electrons. This loss or gain leaves a full outer shell, so the electronic structure of an ion is the same as that of a noble gas (such as helium, neon or argon).

What do metal atoms do when they ionise?

Metal atoms lose the electron, or electrons, in their highest energy level and become positively charged ions.

What do non metal atoms do when they ionise?

Non-metal atoms gain an electron, or electrons, to become negatively charged ions.

When something loses electrons we say that it has been oxidised. When something gains electrons, we say it has been reduced.

What does OIL RIG stand for?

 Oxidation Is Loss of electrons, Reduction Is Gain of electrons.

So in ionic bonding, the metals are oxidised and the non-metals are reduced.

The rate of a reaction can be measured by the rate at which a reactant is used up, or the rate at which a product is formed.

The temperature, concentration, pressure of reacting gases, surface area of reacting solids, and the use of catalysts, are all factors which affect the rate of a reaction.

Chemical reactions can only happen if reactant particles collide with enough energy. The more frequently particles collide, and the greater the proportion of collisions with enough energy, the greater the rate of reaction.

How can you measure the rate of reaction?

You can either measure the rate at which a reactant is used up or measure the rate at which a product is formed

What can you measure?

The measurement itself depends on the nature of the reactant or product:

You could measure the mass of a substance - solid, liquid or gas - is measured with a balance or the volume of a gas is usually measured with a gas syringe, or sometimes an upside down measuring cylinder or burette.

What's the rate of reaction equation?

For example, if 24 cm³ of hydrogen gas is produced in two minutes, the mean rate of reaction = 24 ÷ 2 = 12 cm³ hydrogen / min.

What factors can increase the rate of reaction?

• The temperature is increased
• The concentration of a dissolved reactant is increased
• The pressure of a reacting gas is increased
• Solid reactants are broken into smaller pieces
• A catalyst is used

What gases are in the air?

• nitrogen (78%)
• oxygen (21%)
• argon (0.9%)
• carbon dioxide (0.04%)
• water vapour

How was the early atmosphere formed?

Its early atmosphere was probably formed from the gases given out by volcanoes. It is believed that there was intense volcanic activity for the first billion years of the Earth's existence.

What was the early atmosphere made up of?

The early atmosphere was probably mostly carbon dioxide, with little or no oxygen. There were smaller proportions of water vapour, ammonia and methane. As the Earth cooled down, most of the water vapour condensed and formed the oceans.

How did the proportion of oxygen in the atmosphere increase?

The proportion of oxygen went up because of photosynthesis by plants.

Why did the proportion of carbon dioxide decrease?

The proportion of carbon dioxide went down because:

• it was locked up in sedimentary rocks (such as limestone) and in fossil fuels
• it was absorbed by plants for photosynthesis
• it dissolved in the oceans

The burning of fossil fuels is adding carbon dioxide to the atmosphere faster than it can be removed. This means that the level of carbon dioxide in the atmosphere is increasing.