honors chem - unit four

what is a periodic trend?

A specific pattern in the periodic table that is the result of various physical and chemical properties of elements or elements atoms

why does the current organization of elements allow us to have periodic trends?

these trends exist because of electron configuration, valence electrons, number of energy levels, number of protons and neutrons, etc which are reliant on the set up of the periodic table

what is coulomb’s law?

A law quantitatively describing amount of electrostatic force that two objects exert on each other, causing repulsion or attraction between said objects

why is coulomb’s law relevant to periodic trends?

it describes the electrostatic force between charge particles. this force influences atomic structure and behavior. it helps us to understand periodic trends by showing how the distance between two particles, and the magnitudes of their charges, affect properties of elements on the periodic table

what variables affect the electrostatic force as a result of coulomb’s law?

magnitude of charges and distance

What is atomic radii?

1/2 of the distance between the nuclei of two identical atoms that are considered to have their outer most energy levels tangent with each other. In other words, the size of an atom typically measured in picometers

what are the group and period trends of atomic radiation

Decreases across a period and increases down a group

Why does atomic radiation have the trends it does

period trend - due to increasing positive charge in the nucleus (the addition of protons and increase of atomic number), pulls in electrons, no addition of energy level

group trend - adding energy levels as you go down, outer electrons are shielded from the pull of the nucleus

what is ionization energy?

amount of energy needed to remove a valence electron from an atom (measured in kJ/mol)

what is the trend of ionization energy?

period trend - increases across the period

group trend - decreases down a group

why does ionization energy have the trends it does?

period table - when going across the period, atomic radii decreases, meaning the electrons are closer to the nucleus, making more energy be required to separate electrons from the atom (Coulomb’s law)

group trend - when going from the top to the bottom of the periodic table, energy levels increase in amount, making force of attraction weaker (since furthest electron is more distant)

what is a cation?

atom that has lost a valence electron to become positively charged

what is an anion?

atom gaining a valence electron to become negatively charged

what is electronegativity?

the tendency for an atom to pull in and hold valence electrons from other atoms’ towards its own nucleus

what is the trend for electronegativity?

period trend - increases across a period

group trend - decreases down a group

why is the trend for electronegativity the way it is?

period trend - as you go across the periodic table, there is a significant increase in nuclear charge (specifically positive charge of protons), giving it a higher tendency to attract anything with a negative charge

group trend - there is a “shielding effect” towards the atom when there is a change in energy levels, there is a higher tendency when less energy levels are present

what is atomic mass?

average amount of mass from all stable isotopes of a particular element (usually in amu)

what is the trend of atomic mass?

period trend - increases across a period

group trend - increases down a group

why is the trend for atomic mass the way it is?

period trend - moving from left to right on the periodic table, you increase the number of Protons (with a mass of 1amu). By nature of stability, number of neutrons (1amu) must also increase

group trend - moving from top to bottom of the table, you increase number of Protons (1amu), number of neutrons (1amu) must also increase

what is reactivity?

the desire of an element’s atom to lose/gain valence electrons to become like a noble gas in terms of electron configuration

what are the trends of reactivity for metals?

period trend - decreases

group trend - increases

what is the trend of reactivity for metalloids?

increases down the staircase

what are the trends of reactivity for non metals?

period trend - increases

group trend - decreases

how to determine number of valence electrons in each block?

S and P - group number

F - electron configuration

why can elements in d block have different numbers of valence electrons?

because they use both s and d electrons for bonding

what is an oxidation state?

a number showing how many electrons an atom has gained/lost in a compound

what is valency?

atoms ability to bond with other atoms to create new substances

higher valency = -ic

lower valence = -ous

what is the oxidation rule for elements?

the oxidation number is zero

what is the oxidation rule for monatomic ions?

ions from a single atom equal the charge of the ion

oxidation rule for oxygen

the oxidation number is -2, unless it’s a peroxide, then it’s -1

oxidation rule for hydrogen

oxidation number is 1, unless bonded to a metal, then it’s -1

oxidation rule for halogens

fluorine is always -1

other are -1 unless bonded to oxygen or another halogen

oxidation rule of compounds and ions

sum of oxidation number of atoms in a compound is zero

sum in a polyatomic ion equals charge of the ion

duet rule

an elements atom wants a total of 2 valence electrons in the outermost energy level to be considered unreactive (mainly elements in first two groups)

octet rule

rule in which an elements atom wants a total of 8 valence electrons in the outermost energy level to be considered unreactive (most elements besides first two groups)

what is a mole?

amount of any given substance containing as many particles as there are atoms in 12g of carbon-12

why is the mole important for chemistry?

it measures the amount of substance

who was amedeo avogadro?

an italian chemist determine the amount of particles in one mole of substance

what is molar mass?

mass amount that one mole of a specific pure substance has (written in g/mol)