chemistry Flashcards
what is all matter made of
atoms
what is an element
a substance made up of one type of atom
how are the elements listed in the periodic table
from lowest to highest atomic number
what are the subatomic particles of an atom
protons, neutrons, electrons
what subatomic particle(s) are/is in the nucleus
protons and neutrons
what charge do protons have
positive
what charge do electrons have
negative
what charge do neutrons have
neutral/no charge
what is the atomic number
the amount of protons
what is the mass number
the number of protons + neutrons
how is an isotopic symbol laid out
mass number on top, atomic number on bottom and chemical symbol next to them
what is the mass of an electron
1/1800 of the mass of a proton/neutron
what is the mass of a proton/neutron
1800x the mass of an electron, the same as a neutron
how are electrons arranged
in shells, in energy levels
what is the equation for the maximum amount of electrons in a shell
2n², n is the amount of shells
which shells/electrons have the least energy
the closer to the nucleus the less energy the shell/electrons have
how do electrons fill their shells
electrons begin to fill shells with lowest energy, closest to the nucleus first
what are periods and how many
the horizontal rows, numbered 1 to 7
what are groups and how many
groups are vertical rows, numbered 1 to 18
how are ions formed
an atom loses or gains electrons to have a full valence shell
why do atoms want a full outer shell
to make them stable
what is a cation
a positively charged ion, loses electron/s usually metals
what is an anion
a negatively charged ion, gains electron/s usually non metals
what happens when an element is heated (flame tests)
electrons absorb energy and ‘jump’ to a higher shell (energy level), electron is excited and unstable and releases energy to return to original shell (ground state), this energy is (sometimes) released in form of light
what happens to the energy when an electron goes from a higher shell to a lower one
energy is emitted
what happens to the energy when an electron goes from a lower shell to a higher one
energy is absorbed
how is an isotopic symbol read
top number - mass number
bottom number - atomic number
superscript - charge of ion
what is special about noble gases
they are stable, they have a full outer shell
what is ionic bonding
when a non metal and metal react in a chemical reaction and a cation (metal) and an anion (non metal) are formed
law of conservation of mass
matter cant be created or destroyed in a chemical reaction, all atoms present at the start are present at the end and the mass of the reactants must equal the mass of the products
what happens in a chemical change
a new substance is formed, it is usually difficult to reverse
examples of chemical change
burning toast, cooking an egg, baking a cake (baking part), burning wood, rust
what does cobalt stand for
colour change, odour, bubbles, appearance/disappearance of a solid, light or sound, temperature change
what happens on an atomic level in a chemical reaction
bonds in the reactants are broken, the atoms rearrange and new bonds are formed to make the products
what are the symbols in a chemical equation
s - solid
aq - aqueous (solution/acid/dissolved)
g - gas
l - liquid (usually water only)
what does the subscript represent (in a word equation)
the number of atoms in a molecule (H₂O has 2 H’s and 1 O)
what does the coefficient mean (in a word equation)
the number of each molecule and multiplies the subscripts
what does a balanced equation need
to represent the law of conservation of mass, needs to have the same amount of each atom in the reactants and products
what is the rate of reaction
the speed at which a reaction occurs
how is the rate of reaction measured
how fast the reactants are used up or how fast the products are made
what must occur for a reaction to take place (particles)
particles of different substances must collide
how does collision rate affect reaction rate
the more (successful) collisions in a given time, the faster the reaction
what makes a collision successful
molecules collide with enough energy and have the correct orientation (face each other)
what happens to the rate of reaction over time
the rate decreases, the concentration of reactants decreases, reducing the frequency of collisions
how can the rate of reaction be increased
increase temperature, increase concentration of dissolved reactants, increase surface area of solid reactants and/or use a catalyst
how does temperature affect the reaction rate
higher temperatures cause particles to move faster, they have more energy and are more likely to collide with enough energy, number of successful collisions increases, lower temperatures cause particles to move slower
how does concentration affect the reaction rate
higher concentration means that there are more particles in the same amount of space, particles are more likely to collide and react
how does surface area affect the reaction rate
any reaction involving a solid can only take place on the surface of the solid, if surface area increases there are more collisions
how does a catalyst affect the reaction rate
it speeds up the reaction, the catalyst is unchanged/not used up by the end so isn’t therefore a reactant and can be reused, it provides a surface for the reaction to take place on, therefore increases frequency of collisions
why are catalysts important in some industries
products are made more quickly, reduce the need for high temperatures, can be reused, essential for life, enzymes (biological catalysts)
