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General Chemistry > Atomic Structures and Periodic Trends > Flashcards

Atomic Structures and Periodic Trends Flashcards

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1
Q

atoms

A

atoms are the smallest units of any element. they have a nucleus which contains protons and neutrons, collectively known as the neucleons.

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2
Q

charges

A

protons have a +1 charge

neutrons have no charge and electrons have a -1 charge, these are outside the nucleus!

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3
Q

in every neutral atom, the number of electrons outside the nucleus =

A

number of protons that are in the nucleus.

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4
Q

how are the electrons held in the atom?

A

by electrostatic interaction of the positively charged nucleus.

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5
Q

the number of protons in the nucleus is called ?

A

atomic number Z
This determines what element the atom is .
this can be shown as a subscript

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6
Q

all mass of the atom is due to the mass of the ?

A

nucleus

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7
Q

the number of protons plus the number of neutrons in the nucleus of an atom give the atoms?

A

mass number A

this is written as a superscript!

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8
Q

what are isotopes?

A

two atoms of the same element that differ in their number of neutrons!
if the number of the protons differed then it would not be the same elements!
- isotopes have the same atomic number but diff mass numbers bc their numbers of neutrons are different.

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9
Q

atomic weight

A

is the weighted average of the masses of its naturally occurring isotopes.
remember its the WEIGHTED average

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10
Q

what’s an ion?

A

when a neutral atom gains or looses electrons it becomes charged and the resulting atom is called an ion

  • negatively charged ion is called an anion
  • positively charged- its called a cation
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11
Q

what is the strong nucleur force?

A

a force that holds together the protons and the neutrons
its stronger then the electrical force that’s between charged particles.
the strong nucleur force must overcome the electrical repulsion between the protons.

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12
Q

unstable nuclei are said to be?

A

radioactive! - they undergo transformation to make them more stable - which is called radioactive decay.

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13
Q

what are the three types of radioactive decay?

A

alpha, beta and gamma

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14
Q

what happens in alpha decay?

A

alpha particle is denoted by 4a2 (4 is the superscript and 2 is the subscript). consisting of 2 protons and 2 neutrons. this is equivalent to helium 4 nucleus.
- alpha decay will reduce the atomic number by 2 , and the mass number by 4.
- alpha particles are emitted with high energy but this energy is lost due to particle travelling through matter and air.
as a result, particles do not typically travel far, and can be stopped by the outer layers of human skin or a piece of paper.

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15
Q

what happens in beta decay?

A

there are three TYPES of beta decay.
so B-
B+ and electron capture.
each type involves conversion of a neutron into a proton.
beta particles are more dangerous then alpha as they are significantly less massive. so they have more energy and greater penetrating ability.

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16
Q

what happens in beta - decay?

A

when an unstable nucleus has too many neutrons , it can confert a neutron to protons and an electron ( which is the B- particle).
the atomic number will be 1 greater but the mass number will remain the same.
this is the most common type of beta decay so if the exam mentions beta decay it is most likely this one

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17
Q

what is B+ decay?

A

when an unstable nucleus has too few neutrons , it will convert a proton into a neutron and a positron which is ejected. this is known as B+ decay. the positron is the electron antiparticle. the atomic number will be 1 less but the mass number will be the same.

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18
Q

electron capture

A

another way for an unstable nucleus to increase the neutrons is to grab an electron from the closest shell and use it to convert proton into a neutron.
electron capture will cause the atomic number to be reduced by 1 while the mass number stays the same.

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19
Q

what is the common thing in all types of beta decay?

A

the mass number will stay the same

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20
Q

what happens in gamma decay?

A

nucleus in an excited state can relax to its ground state by emitting energy in the form of photons. these photons are called gamma photons.
gamma photons have neither mass or a charge, therefore penetrate matter most effectively.
the mass number is not changed and neither is the atomic number.
alpha and beta decay change the identity of the nucleus but in gamma decay that dosent happen. gamma decay is simply an expulsion of energy.

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21
Q

half life

A

time it takes for half of the sample to decay.
the amount of substance will decrease exponentially with time.
k= ln2 (t1/2)

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22
Q

what is nuclear binding energy?

A

energy released when protons and neutrons are bound together by strong force to form the nucleus.
when the nucleons (neutrons and the protons) bind together to form a nucleus, some mass is converted to energy . the mass of the combined nucleus is less then the sum of the masses of all its nucleons individually. the difference is the mass defect

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23
Q

mass defect

A

this is the nuclear binding energy. this is always positive

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24
Q

what is 1 kg in joules?

A

9x10^16 J

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25
Q

emission spectra

A

gives an energetic fingerprint of the element because it consists of unique sequence of bright lines that correspond to specific wavelengths and energies. the energies of photons are related to the frequency and wavelength

26
Q

E=

A 
hf = h (c/wavelength ) 
h= planks constant (6.63 x10^-34 j.s) c is the speed of light 3x 10^8 m/s)
27
Q

the Bohr model of the atom

A

distance from the nucleus is related to the energy of the electrons . electrons with greater energy orbited the nucleus at greater distances.
electrons have quantized energy states they can’t just assume any arbitrary energy state.
bohr atom is one that contains only 1 electron

28
Q

what is ground state?

A

n=1

29
Q

EXCITED state

A

when an electron absorb a photon it jumps to a higher energy level.

30
Q

formula for calculating the energies of the levels

A

En = (-2.178 x 10^-8J) /n^2

31
Q

why is the bohr model not sufficient?

A

Bohr model does not to do a good job of predicting the atomic spectra of many electron atoms. the bohr model
cannot describe the electron-electron interactions that exist in many electron atoms.
the quantum model was developed to account for these differences.

32
Q

quantum model.

A

the electron energy levels are quantized.
the quantization is described by a unique address for each electron, consisting of four quantum numbers designated as the shell, sub shell, orbital and spin.

33
Q

the energy shell (n)

A

an electron in a higher shell has greater amount of energy and a greater distance from nucleus.

34
Q

the energy sub shell (orbital)

A

3d region around the nucleus in which the electron is most likely to be found.
- a sub shell in an atom is comprised of one or more orbital and is denoted by letters s,p,d,f which describe the shape and the energy of the orbital. the orbitals in the sub shells get progressively more complex and higher in energy in the order listed above.

35
Q

the orbital orientation

A

the number of orientations increase by two in each successive sub shell. for example) the s sub shell contains 1 orientation and the p sub shell has 3. (px,py,pz)

36
Q

the electron spin

A

every electron has 2 possible spin state bc of this every orbital can accommodate a max of 2 electrons. one spin up and one spin down.

37
Q

what are the three basic rules of electron configurations?

A

aufbau principle
hands rule
pauli exclusion principle

38
Q

aufbau principle

A

electrons occupy lowest energy orbitals first.

39
Q

hunds rule

A

electrons in the same sub shell occupy the available orbitals singly before pairing up

40
Q

pauli exclusion principle

A

there can be no more then two electrons in any given orbital

41
Q

diamagnetic atom

A

an atom that has all of its electrons spin paired
- must have an even number of electrons and have all sub shells filled.
since all electrons are spin paired, the individual magnetic fields that they create cancel and there will no net magnetic field! so it would be REPELLED by an external magnetic field.

42
Q

paramagnetic

A

if an atoms electrons are not all spin paired, its paramagnetic. these are attracted to external magnetic fields.

43
Q

period

A

horizontal row

44
Q

group

A

vertical column

45
Q

when you are in the d block subtract one from?

A

the period number

so the first row of the d block is in period 4 but strict 1 so it will be in third period instead

46
Q

every energy level adds a new sub shell

A

so n=2 would be s, p
n=3 would be s,p,d subshells
there are 1,3,5 orbitals in these subshells = total of 9 orbital .
each orbital can have 2 electrons so a max of 18 electrons in the n=3 energy level

47
Q

some atoms can achieve a lower energy state by having a half filled or a filled d sub shell

A

examples include : chromium , copper, molybdenum, silver and gold

48
Q

electrons that are removed from an atom come from the valence shell (highest n level) and the highest energy orbital within that level

A

EXCEPTION is the transition metals , they will loose electrons from from the s sub shell before the D

49
Q

electron configuration of an excited oxygen atom?

A

excited atom is not an ion, electrons are not lost or gained, they simply jump to a higher energy levels within the atom.

50
Q

valence electrons

A

valence electrons are responsible for an atoms properties and chemical behaviours.

51
Q

what are mettaloids?

A

properties of both metal and non metals.

B, Si, Ge, As, Sb, Te, Po

52
Q

shielding

A

each filled shell between the nucleus and the valence electrons shields or protects the valence electrons from the full effect of the positively charged protons in the nucleus.

53
Q

atomic radius

A

if you go across the period, the protons will increase and the pull on the outermost electrons will increase. new shells are initiated only at the beg of the period.
so as we are going across the period, electrons are being added but new shells are not, therefore valence electrons are more and more tightly bound to the atom . so the atomic radius will decrease across the period.

54
Q

atomic radius

A

however, as we go down a group, new shells are added and the valence electrons will get shielding so now they will feel a smaller effective nucleur charge (Zeff) therefore as you go down a group, the radius will increase due to shielding.

55
Q

cation radius

A

will dec bc we loose electrons , its smaller then the neutral atom radius and the anion radius

56
Q

anion radius

A

will inc bc electron is added. bigger then neutral atom radius and the cation radius.

57
Q

ionization energy

A

amount of energy needed to remove the least tightly bound electron from an atom .
as we move left to right across the periodic table, the ionization energy will increase since the valence electrons are more tightly bound.

58
Q

what is the second ionization energy?

A

energy required to remove the least tightly bound electron from a cation ! this is greater then the first ionization energy.

59
Q

electron affinity

A

become more negative as we move to the right across a row or up a group (except noble gases).
becoming more negative means: energy is released when an electron is added.

60
Q

electronegativity

A

measure of an atoms ability to pull electrons to itself.
increases as we go from left to right across a period
as we go down a group, electronegativity would decrease.
know FONClBrISCH

61
Q

acidity

A

measure of how well a compound will donate a proton , accept electron.
the more electronegative the element bearing the negative charge, the more stable the anion will be.
therefore acidity will increase from left to right across period.
however, the vertical trend for acidity will depend on the size of the anion.
the larger the anion the more the negative charge can be stabilized. therefore acidity will increase down the group.

62
Q

TRENDS

A

ionization energy, electron affinity and electronegativity
will increase to the right and up

acidity will inc down

General Chemistry (10 decks)

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