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Applied Science > Chemistry Unit 1 - Periodicity and properties of elements > Flashcards

Chemistry Unit 1 - Periodicity and properties of elements Flashcards

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1
Q

what is an atom?

A

-the smallest particle of a chemical element that can exist

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2
Q

what is an element?

A

-a substance consisting of atoms which all have the same number of protons i.e. the same atomic number

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3
Q

what is meant by atomic number?

A

-the number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table

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4
Q

what are isotopes?

A

-atoms of the same element with the same number of protons, but different numbers of neutrons and hence different mass numbers

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5
Q

what is meant by mass number?

A

-the total number of protons and neutrons in the nucleus of an atom
-different isotopes of the same element have different mass numbers

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6
Q

what is meant by relative atomic mass ( Ar )?

A

-the mean mass of the atoms of an element compared with 1/12 of the mass of a carbon-12 atom
-it is an average of the mass numbers of all the different isotopes of that element

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7
Q

how is relative atomic mass calculated?

A

-Ar = ( isotopic mass x % abundance ) + ( isotopic mass x % abundance ) / 100
-multiply the mass number of each isotope by its relative abundance
-add them all together
-divide by 100 if abundance is in %

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8
Q

why is the relative atomic mass not always a whole number?

A

-different isotopes of the same element have different mass numbers and the relative atomic mass is an average of the mass numbers of all these isotopes

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9
Q

what was Bohr’s theory?

A

-an atom has a small, positively charged central nucleus, orbited by electrons at fixed energy levels ( i.e. distances from the nucleus ) which are split into subshells

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10
Q

what is the structure of an atom?

A

-a small, positively charged central nucleus which contains protons and neutrons, orbited by electrons in shells which are made up of subshells ( s, p, d )

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11
Q

what is the nucleus of an atom?

A

-the positively charged central core of an atom, containing protons and neutrons and nearly all of its mass

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12
Q

what are the relative masses and charges of protons, neutrons and electrons?

A

-proton = 1, +1
-neutron = 1, 0
-electron = 0.0005 or 1/1836, -1

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13
Q

how can the number of protons, neutrons and electrons of an element be calculated?

A

-protons = atomic number
-neutrons = difference between mass ( big ) number and atomic ( small ) number
-electrons = number of protons

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14
Q

how are elements arranged in the periodic table?

A

-in order of increasing atomic number i.e. proton number, in rows called periods ( period number = number of electron shells )
-elements with similar properties are placed in the same vertical columns called groups ( group number = number of outer shell electrons )
-the order of elements is due to their atomic number, but an element’s position is due to its electronic structure and is dependent on its outermost electron shell
-metals on the left, nonmetals on the right and transition metals in the middle
-split into three blocks = s-block ( groups 1 and 2, along with H and He ), p-block ( groups 3-8 except He ) and d-block ( transition metals )
-s, p and d blocks indicate the subshell being filled with electrons as you go across the table, and the position of an element in a block is determined by the highest subshell occupied by electrons in that element

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15
Q

what is an electron shell?

A

-a group of atomic orbitals with the same principal quantum number, n
-also known as a main energy level

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16
Q

what is a subshell?

A

-a group of orbitals of the same type within a shell ( s, p or d )

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17
Q

what is an orbital?

A

-a region within an atom that can hold up to 2 electrons with opposite spins ( s, p or d )
-an s orbital is spherical in shape whereas a p orbital is dumb-bell shaped

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18
Q

how many electrons can each subshell hold and why?

A

-s subshell = 2, because it has 1 orbital
-p subshell = 6, because it has 3 orbitals
-d subshell = 10, because it has 5 orbitals
-f subshell = 14, because it has 7 orbitals

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19
Q

how many electrons can the first four shells hold and why?

A

-1st shell = 2, because it has an s subshell ( 1s )
-2nd shell = 8, because it has s and p subshells ( 2s, 2p )
-3rd shell = 18, because it has s, p and d subshells ( 3s, 3p, 3d )
-4th shell = 32, because it has s, p, d and f subshells ( 4s, 4p, 4d, 4f )

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20
Q

what is the order of filling orbitals?

A

-1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^10, 4p^6 etc.

21
Q

what are the rules for arranging electrons in subshells?

A

-start at the lowest shell and add electrons one at a time
-fill each subshell before starting on the next ( the Aufbau principle )
-fill the the 4s subshell before the 3d subshell because it is higher in energy when occupied
-fill each orbital singly in a subshell before pairing electrons
-paired electrons have opposite spins to reduce repulsion, so they are shown as arrows pointing in opposite directions

22
Q

what is a compound?

A

-a substance that is composed of two or more separate elements
-e.g. H2O, NaCl, CO2

23
Q

what is a molecule?

A

-a group of atoms chemically bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction
-e.g. H2O ( compound ), Cl2 ( element ), C2H6O ( compound )

24
Q

what is an ion?

A

-an atom or molecule with a net electric charge due to the gain or loss of one or more electrons
-e.g. Cl^-, CO3^2-, Na^+

25
Q

what is the formula of a nitrate ion?

A

-NO3^-

26
Q

what is the formula of a carbonate ion?

A

-CO3^2-

27
Q

what is the formula of a sulfate ion?

A

-SO4^2-

28
Q

what is the formula of a hydroxide ion?

A

-OH^-

29
Q

what is the formula of an ammonium ion?

A

-NH4^+

30
Q

what is the formula of a zinc ion?

A

-Zn^2+

31
Q

what is the formula of a silver ion?

A

-Ag^+

32
Q

what is a monoatomic ion?

A

-formed by the gain or loss of electrons to the valence ( outermost ) shell in a single atom
-e.g. chloride, sodium, calcium

33
Q

how is the charge on a monoatomic ion linked to its position in the periodic table?

A

-group 1 = 1+
-group 2 = 2+
-group 3 = 3+
-group 5 = 3-
-group 6 = 2-
-group 7 = 1-

34
Q

why can’t the charges on ions of transition metals be predicted?

A

-they can form several stable ions
-e.g. iron can be Fe^2+ or Fe^3+

35
Q

what is a molecular ion?

A

-formed by the gain or loss of elemental ions such as a proton, H^+
-e.g. nitrate, carbonate, sulfate, hydroxide, ammonium

36
Q

what is meant by relative formula mass ( Mr )?

A

-the sum of the relative atomic masses of all the atoms in a formula

37
Q

what is meant by mole ( n )?

A

-the amount of any substance containing 6.02 x 10^23 particles

38
Q

what is the mass of one mole of an element equal to?

A

-its relative atomic mass in g
-e.g. 24.3 g of magnesium contains 1 mole of atoms

39
Q

what is the formula linking mass, moles and relative formula mass?

A

-m = n x Mr
-mass ( m ) in g = moles ( n ) in mol x relative formula mass ( Mr )

40
Q

what is the Avogadro constant?

A

-the number of atoms, molecules or ions in one mole of a substance
-the value of the constant is 6.02 x 10^23

41
Q

what is the formula linking the number of particles, the Avogadro constant and moles?

A

-P = n x Av
-number of particles ( P ) in atoms, molecules or ions = moles ( n ) in mol x the Avogadro constant ( Av )

42
Q

what is meant by molar mass?

A

-the mass per mol of a substance in g mol^-1
-it is equal to its relative formula mass

43
Q

what is the formula linking mass, moles and molar mass?

A

-m = n x M
-mass ( m ) in g = moles ( n ) in mol x molar mass ( M ) in g mol^-1

44
Q

what is meant by empirical formula?

A

-the simplest / smallest whole number ratio of the atoms of each element in a compound

45
Q

how is empirical formula calculated?

A

-calculate moles of each element by mass ( if in %, do mass in 100g ) / Ar
-divide moles by the smallest value to get a ratio
-adjust to make the ratios whole numbers by rounding up or doubling to get rid of halves

46
Q

what is meant by molecular formula?

A

-the actual number of atoms of each element in a compound

47
Q

how is molecular formula calculated?

A

-calculate Mr of empirical formula
-divide relative molecular mass by Mr of empirical formula
-multiply this by empirical formula

48
Q

what is meant by stoichiometry?

A

-the ratio, of the amount in moles, of each substance in a chemical reaction ( the balancing numbers in front of each substance )

49
Q

how is the mass ( in g ) of a substance calculated from the mass of another substance in the same reaction?

A

-balance equation to find molar ratio
-calculate moles of given by mass / Ar
-calculate moles of asked using molar ratio
-calculate Mr of asked
-calculate mass of asked by moles x Mr

Applied Science (3 decks)

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