Chemistry

periodic law

the law stating that certain chemicals and physical properties repeat themselves every eight elements when the elements are arranged in order of increasing atomic number

period

a row in the periodic table

group

a column in the periodic table

monatomic ion

an atom made of exactly one atom, it is an atom that has an unequal amount of protons and electrons

3 types of chemical bonds

ionic, covalent, metallic

ionic bonds

bonds that are formed when atoms of different electronegativities transfer electrons to each other, resulting in the formation of ionic compounds that are held together by electrostatic attraction

process of ionic bonding

a metal atom transfers one or more electrons to a non-metal atom, the metal atom turns into a cation and the non-metal atom turns into an anion, because opposite charges attract the two atoms are held together by an electrostatic attraction

properties of ionic compounds

• high melting + boiling points (indicates strong bond strength)

• most are crystalline solids at room temperature

• form in regular geometric patterns

• hard + brittle

naming ionic compounds

metal (usual) + non-metal ("ide" ending)

subscript

an number used to show how many atoms of an element are present

coefficient

a number placed before a formula in a chemical equation

polyatomic ions

a charged species consisting of two or more atoms covalently bonded together

transition metals

metals on the periodic table that have can have multiple different valencies enabling them to make a wide variety of ions with different charges

balanced equation

an equation that has the same numbers of each type of atom on both sides of the equation

the law of conservation of matter

the rule stating that the number of atoms in a chemical reaction remain the same

physical change

a change in which no new substances are formed, involves the changes of properties such as:

• positions

• shape

• size

• state

chemical reactions (1)

a reaction in which new substances form, includes typical signs such as:

• release of light/sound

• formation of a new gas

• change in colour

• disappearance of a solid

• formation of a new solid

• change in temperature

chemical reactions (2)

the transformation of one or more substances into new substances, these may be either elements or compounds

reactants

the materials in a chemical reaction that react with each other

products

the new substances formed by a chemical reaction

how atoms are rearranged in a chemical reaction

bonds are broken in the reactants and new bonds are formed to create the products, the same atoms remain after the reaction has taken place (locom)

endothermic reactions

reactions that absorb energy, resulting in the decrease of the surrounding temperature the energy released is less than the activation energy

exothermic reactions

reactions that release energy, resulting in the increase of the surrounding temperature the energy released is greater than the activation energy

the difference between exothermic and endothermic reactions

all reactions require bonds to be broken (this requires energy) and new bonds to be made (this releases energy), what differentiates exo and endothermic reactions is whether the amount of energy released when the new bonds form is greater or less than the energy required to break the bonds

activation energy

the energy required to break bonds and start a reaction, amount needed differs for different reactions and is required for both exothermic and endothermic reactions

acid

a substance with a pH less than 7 that releases hydrogen ions when dissolved in a solution

properties of acids

sour, react with metals, can be corrosive

common acids

sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid, acetic acid, carbonic acid

base

a substance with a pH greater than 7 that releases hydroxide ions when dissolved in a solution

properties of bases

bitter, slippery

common bases

lithium hydroxide, sodium hydroxide, potassium hydroxide, barium hydroxide, strontium hydroxide

neutralisation reaction

a chemical reaction in which an acid reacts with a base to produce salt and water

chemical salt

a molecule containing a metal cation and a non-metal anion

pH scale

measures the concentration of hydrogen ions in a solution, translates to power hydrogen scale

indicator

a substance that changes colour in the presence of an acid or base eg. litmus paper, universal indicator

acid + metal reactions

reactions in which an acid reacts with a metal to create salt and hydrogen gas

acid + carbonate reactions

a reaction in which an acid reacts with a carbonate to create salt, water and carbon dioxide