Acid and Bases notes/definitions

Chem exam prep

Group

Vertical row, tells us number of valence electrons.

Period

Horizontal row, tells us number of electron shells an atom has.

Ions

Atoms form these to become stable and gain a full valence shell. If an atom loses electrons to become stable it’s an anion, if an atom gains electrons it’s a cation.

Anion

Positively charged

Cation

Negatively charged.

Ionic bonding

When a metal atom reacts with a non metal atom. Electrons are transferred forming a cation and anion. These oppositely charged ions are attracted to each other and form an ionic bond.

Metalic bonding

Is when metal atoms are attracted to other metal atoms of the same element. The attraction is described as electrostatic attraction between the cations and the sea of delocalised electrons.

Covelant bonding

When a non metal atom bonds to another non metal atom. Electrons are shared in a covelant bond. They are molecular substances and covelant bonds never break, only intermolecular forces break.

molecular substances

An individual molecule consisting of non metal atoms held together by strong covelant bonds. It consists of of individual molecules held together by weak intermolecular forces. It has a low melting/boiling point.

Metalic solids

Are metal atoms/cations that are held together in a 3D lattice by strong metalic bonds. Valence electrons are loosely held (delocalised), and can move around easily between atoms. It has high melting/boiling point.  

Ionic solids

Are oppositely charged cations and anions that are held together in a 3D lattice by strong electrostatic attraction (ionic bonds). It has a high melting/boiling point.

Melting/boiling point

Is a measure of heat energy required to break some of the attractive forces between the particles.

Acids

Release hydrogen ions when in contact with water. They form solutions with higher concentration of hydrogen ions than hydroxide ions. Turn blue litmus red.

Bases

Form solutions with higher concentrations of hydroxide ions than hydrogen ion. Turns red litmus blue. Soluble bases are alkalis.

Alkalis

Are bases that dissolve in water to form a solutions which contains hydroxide ions. (They’re soluble in water).

Neutralisation

When an acid reacts with a base.

Collision theory

Particles must collide with sufficient energy and the correct orientation in order to react. Reactions can occur quickly or slowly. When reaction rate increases this means the frequency of successful collisions has increased.

Concentration

Is the number of particles in a given volume. Increasing this means there are more particles in a given volume, which means there will be more frequent successful collisions and the rate of reaction will increase. Measured in mole per litre.

Tempreture

Is a measure of the amount of kinetic energy particles have. When increased the particles have more kinetic energy, and move faster. Therefore, there will be a greater frequency of successful collisions, which increases the reaction rate.

Catalyst

Increases rate of reaction by providing an alternative pathway with lower activation energy. This means that more particles collisions will have enough energy to overcome the activation energy barrier, resulting in more successful collisions per second.

Surface area

Is the number of particles exposed for collisions. Greater surface area means more particles are available for collisions. This increases the frequency of successful collisions, increasing the rate of reaction.