Chemistry (main?)

What are the three states of matter?

Solid, liquid and gas.

What is a cation?

Cations are positively charged ions formed by losing electrons

What is an Anion?

Negatively charged ions formed by gaining electrons

Why do anions and cations attract each other to form ionic bonds?

Because they carry opposite electrical charges, they strongly attract each other to form ionic bonds.

What is the formula for mass from moles?

Mass (g) = Relative formula mass (g/mol) x amount (mol)

Covalent bond for CH4? (4 electrons on outer shell of C)

Ionic bond diagram?

Every mole contains the …

Same numbers of particles/ atoms etc

Solute vs Solvent vs Solution

A solute is the substance that gets dissolved, a solvent is the substance that does the dissolving, and a solution is the mixed combination of both

What does ionic bonding form?

They form giant ionic lattices. (regular 3d structures of oppositely charged ions)

What happens during ionic bonding.

A metal atom loses one or more valence electrons (becoming a positive ion, or cation) and a non-metal atom gains those electrons (becoming a negative ion, or anion).

What are the properties of ionic compounds?

They have strong ionic bonds (electrostatic forces), giving them high melting and boiling points. They conduct electricity when molten or dissolved in water.

What is a covalent bond?

A shared pair of electrons between non-metal atoms.

Why does Fluorine make one covalent bond?

Fluorine has 7 electrons in its outer shell, so it only needs to share 1 pair of electrons (1 more electron) to achieve a full, stable outer shell.

Why does an oxygen atom form two covalent bonds?

Oxygen is in Group 6, so it has 6 outer electrons and needs 2 more to get a full outer shell. When bonding with another non-metal, it shares 2 pairs of electrons, forming two covalent bonds.

Why is the formula for magnesium chloride MgCl₂ instead of MgCl?

Magnesium is in Group 2, so it loses 2 electrons to form an Mg²⁺ ion. Chlorine is in Group 7, so each atom only gains 1 electron to form a Cl⁻ ion, meaning two chloride ions are needed to balance the 2+ charge.

What happens to a sodium atom when it becomes an ion?

It loses its single valence electron on it’s outer shell to achieve a stable, full outer shell.

What is distilled water?

Distilled water is pure water (H₂O) that has had all of its impurities, minerals, and contaminants removed through the process of distillation.

What compound is distilled water?

It is a pure chemical compound, not a formulation or a mixture.

What’s a formulation?

A formulation is a mixture designed to do a specific job such as an alloy

What are the steps for chromatography?

• Pencil line: Bottom of paper (won't run).

• Spot sample: Onto the pencil line.

• Solvent level: Must be below the line.

• Lid on: Prevents solvent evaporation.

• Mark front: Pencil mark at highest solvent point.

• Dry & View: Dry paper; use UV if invisible.

• \(R_{f}\) value: Spot distance ÷ Solvent distance.

What’s the mobile phase?

The phase that moves continuously through or over the system.

What’s the stationary phase?

The phase that remains fixed in place and does not move.

What is the Rf value?

(substance = ink ex.)

Describe an experiment where you can measure the melting point of ice.

What’s an alloy?

An alloy is a solid mixture of two or more chemical elements, where at least one of them is a metal

Define the structure of a diamond.

Melting point is around 3550 and it does not conduct electricity.

Approximate size of an atom?

1 × 10 to the power of -4

What’s the subscript?

The small number written below and to the right of an element symbol within a chemical formula.

What is a coefficient?

The large number placed in front of a chemical formula. It tells you how many total molecules, formula units, or moles of that substance are involved in a reaction.

How do you find what ion radium forms when it becomes stable, and why?

It sits in Group 2 of the periodic table, meaning it has two electrons on its outer shell. To become stable, a neutral radium atom loses those two outer electrons to form a +2 ion.

What does a period show?

A period is a line that runs horizontally which shows you exactly how many electron shells (energy layers) an atom has. It also tracks the step-by-step addition of one electron to that outer shell as you read the row from left to right.

How are particles arranged in a solid?

They are closely packed in a fixed, regular arrangement and vibrate about fixed positions.

How are particles arranged in a liquid?

They are close together but arranged randomly and can move past one another.

How are particles arranged in a gas?

They are far apart, randomly arranged and move rapidly in all directions.

What is the particle model?

The particle model states that all matter is made up of tiny, moving particles.

⭐ How would you draw the particle arrangements in solids, liquids and gases?

Solid: closely packed regular particles. Liquid: closely packed irregular particles. Gas: widely spaced random particles.

What happens to particles when a substance changes state?

They gain or lose energy, changing their movement and arrangement.

What is melting?

The change of state from solid to liquid.

What is freezing?

The change of state from liquid to solid.

What is evaporation?

The change of state from liquid to gas at the surface of a liquid.

What is boiling?

The change of state from liquid to gas throughout the liquid at its boiling point.

What is condensation?

The change of state from gas to liquid.

What is sublimation?

The direct change from solid to gas without becoming liquid.

What is diffusion?

The spreading out of particles from an area of higher concentration to an area of lower concentration.

What is an element?

A substance made of only one type of atom.

What is a compound?

A substance containing two or more different elements chemically bonded together.

What is a mixture?

A mixture consists of two or more elements or compounds that are physically combined together and not chemically bonded

What is an atom?

The smallest part of an element that can take part in a chemical reaction.

⭐ What are the three subatomic particles and their charges?

Proton: +1. Neutron: 0. Electron: −1.

Where are protons and neutrons found?

In the nucleus.

Where are electrons found?

In shells or energy levels around the nucleus.

What is the atomic number?

The number of protons in an atom.

What is the mass number?

The total number of protons and neutrons.

How do you calculate the number of neutrons?

Mass number − atomic number.

⭐ How do you work out the electronic structure of an atom?

Use the atomic number to find the number of electrons, then fill the shells. For the first 20 elements, the pattern is 2, 8, 8, 2.

What is an isotope?

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

Example: Carbon-12 (6 protons, 6 neutrons) and Carbon-14 (6 protons, 8 neutrons) — both are carbon with 6 protons, just different numbers of neutrons.

What is an ion?

An atom or group of atoms with an electrical charge because it has gained or lost electrons.

How is a positive ion formed?

An atom loses electrons.

How is a negative ion formed?

An atom gains electrons.

What is a neutral atom?

An atom with equal numbers of protons and electrons.

What is a proton?

A positively charged particle found in the nucleus.

What is a neutron?

An uncharged particle found in the nucleus.

What is an electron?

A negatively charged particle found in shells around the nucleus.

What is a nucleus?

The small, dense centre of an atom containing protons and neutrons.

What is an electron shell?

An energy level around the nucleus in which electrons are found.

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.

⭐ What did the plum pudding model suggest about atomic structure?

It suggested that an atom was a sphere of positive charge with negative electrons embedded in it.

⭐ What did Rutherford's alpha scattering experiment show about the atom?

Most alpha particles passed through, but a few were deflected. This showed that atoms are mostly empty space with a small, dense, positively charged nucleus.

⭐ How did the nuclear model differ from the plum pudding model?

It proposed a small, dense, positively charged nucleus with electrons around it, rather than positive charge spread throughout the atom.

How do you calculate relative formula mass?

Add together the relative atomic masses of every atom in the formula.

What is relative formula mass?

The sum of the relative atomic masses of all atoms in a formula.

What is relative molecular mass?

The sum of the relative atomic masses of all atoms in a molecule.

What is an empirical formula?

The simplest whole-number ratio of atoms of each element in a compound.

How do you calculate an empirical formula from experimental data?

Convert each element's mass into moles, divide by the smallest number of moles, then simplify to a whole-number ratio.

What is the difference between a molecular formula and an empirical formula?

A molecular formula gives the actual number of each atom in a molecule. An empirical formula gives the simplest ratio.

What is a pure substance in chemistry?

A single element or compound that is not mixed with other substances.

How can melting point data help identify a pure substance?

A pure substance has a sharp, fixed melting point, while an impure substance usually melts over a range.

What is filtration?

A method used to separate an insoluble solid from a liquid.

⭐ How does filtration work?

The mixture is poured through filter paper. The liquid passes through as the filtrate, while the solid remains as the residue.

What is crystallisation?

A method used to obtain crystals of a dissolved solid from a solution.

⭐ How can crystals be obtained from a solution?

Heat the solution to evaporate some solvent, allow it to cool so crystals form, then filter and dry the crystals.

What is simple distillation?

A method used to separate a solvent from a solution by evaporation and condensation.

⭐ How does simple distillation work?

The solution is heated, the liquid evaporates, then vapour passes through a condenser and cools into a collected liquid.

What is fractional distillation?

A method used to separate a mixture of liquids with different boiling points.

⭐ How does paper chromatography separate substances?

A solvent moves through paper and carries dissolved substances at different speeds, separating them.

⭐ How do you calculate an Rf value?

Rf = distance travelled by the substance ÷ distance travelled by the solvent front.

What does a chromatogram show?

The substances present in a mixture and how they have separated.

How can chromatography help identify a pure substance?

A pure substance produces one spot, while a mixture usually produces more than one spot.

What is an Rf value?

The ratio of the distance travelled by a substance to the distance travelled by the solvent front.

What is an element?

A substance made from only one type of atom.

What is a metal?

An element that generally conducts heat and electricity and is malleable.

What is a non-metal?

An element that generally does not conduct heat or electricity well and is often brittle when solid.

What is electronic structure?

The arrangement of electrons in shells around an atom's nucleus.

⭐ How do you draw the electronic structure of an element?

Use its atomic number to find its electrons and arrange them in shells.

How are ions formed?

Atoms gain or lose electrons to achieve a more stable electronic structure.

⭐ How do you draw an ionic bonding dot-and-cross diagram?

Show the transfer of electrons from the metal to the non-metal, with the resulting ions in brackets and their charges.

What is ionic bonding?

An ionic bound is the attractive electrostatic force between positive metal ions and negative non metal. (have to be opposite ions and charges)

What is a simple molecular substance?

A substance made of small molecules with strong covalent bonds within each molecule and weaker forces between molecules.