Chemical changes and structure Flashcards
atoms are made from
protons, neutrons, and electrons
where are the electrons found
in the atoms orbit
atoms have an equal number of protons and…
electron
what does the atomic number tell us
how many protons an atom has
what does the mass number tell us
the total number of protons and electrons
what are isotopes
different forms of the same element but with a different number of neutrons
what is relative atomic mass
the average mass of an element, taking into account all the isotopes
what is valency
the number of electrons an atom of an element uses to combine with others
ions are made when…
electrons are transferred
how are negative and positive ions formed
positive ions are formed when an atom loses electrons
negative ions are formed when an atom gains electrons
how are ionic bonds formed
when a metal and non-metal react together they form a positive and negative ion.
these ions are strongly attracted to eachother, which is called an ionic bond
what structure do ionic compounds have
regular lattice
why do ionic compounds have high melting and boiling points
because there are strong ionic bonds between the ions
what are covalent bonds
where atoms share electrons with each other to have a full outer energy level
why are covalent bonds very strong
the positively charged nuclei of the atoms are attracted to the shared electrons
what are diatomic molecules
covalent molecules containing only two atoms
what are the diatomic elements
H2, N2, O2, F2, Cl2, Br2, I2
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why are the melting and boiling points of covalent molecular substances low
because the forces of attraction between the molecules are weak
what determines the shape of covalent molecular substances
the number and direction of bonds around the central atom
what is the gram formula mass
the average masses of all the atoms or ions in a compound added together
what is a base
substance that neutralises an acid
what solution can be made by dissolving a soluble base in water
an alkaline solution
what solution can be made by dissolving a soluble non-metal oxide in water
an acidic solution
what ions do acids form in water
H+ ions
what ions do alkalis form when dissolved in water
OH- ions
what products are produced when an acid and a base react together
salt + water
what are the most common salts and acids
hydrochloric acid, sulfuric acid, nitric acid.
chloride salt, sulfate salt, nitrate salt
what products are produced when an acid, metal oxide or hydroxide react together
salt + water
what are spectator ions
ions that remain unchanged after the reaction
what are titrations used for
to analyse the concentration of solutions. titrations tell us exactly how much of an acid is needed to neutralise an alkali/ vice versa
what pH value would a neutral solution have
7
describe the relationship between the concentration of H+ ions and pH
the higher the concentration of H+ ions a compound has, the more acidic it is
what is the rate of a chemical reaction measuring
how frequently particles collide
what are the four factors that affect the rate of reaction
temperature, concentration, surface area, and the presence of a catalyst
why does temperature affect the rate of a reaction
because an increase in temperature is an increase in particle speed, causing collisions to happen more frequently
the rate of a reaction can be measured in different ways, such as…
change in mass, volume of gas given off or precipitation and colour change
