Atomic Foundations of Matter Mind Map

The law of conservation of mass states that during a chemical change, the total mass of reactants is equal to the total mass of products.

When a question gives masses before and after a reaction, add all reactant masses and all product masses before comparing.

The law of constant proportions states that a pure chemical compound always contains the same elements combined in the same fixed ratio by mass.

For mass-ratio questions, reduce the given masses to the simplest ratio and check whether the ratio is constant.

Atoms combine with other atoms by losing, gaining, or sharing electrons so that they can become more stable.

Mention outermost-shell stability and the method of combination: loss, gain, or sharing of electrons.

Ionic bonding is the chemical bonding formed by transfer of electrons from one atom to another, producing oppositely charged ions that attract each other strongly.

For properties, write strong electrostatic attraction for high melting point and mobile ions for conductivity in molten or aqueous state.

Covalent bonding is the chemical bonding formed when atoms share one or more pairs of electrons.

For covalent bonding answers, mention sharing of electron pairs and show shared electrons clearly in dot diagrams.

Writing chemical formulae means representing a compound using symbols of elements or radicals and the correct number of each particle needed to balance valencies or charges.

Write ions with charges first, criss-cross charge numbers, remove charge signs, and reduce the ratio if needed.

Molecular mass is the sum of the atomic masses of all atoms present in one molecule of a substance.

Underline each subscript and multiply before adding; do not add atomic masses only once.

Formula unit mass is the sum of the atomic masses of all ions or atoms shown in the formula unit of an ionic compound.

First identify whether the compound is ionic. If it is ionic, use the term formula unit mass and calculate from the formula.

Ionic and covalent compounds differ in properties because ionic compounds have ions in a lattice, while covalent compounds usually have molecules formed by shared electrons.

For comparison answers, write property plus reason: high melting point due to strong ion attraction, conductivity due to mobile ions, and poor conductivity of covalent compounds due to neutral molecules.