1.1 Basic ideas about atoms, first half

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  • Created by: Danielle
  • Created on: 03-12-13 18:51
What is an atomic number?
the number of protons in the nucleus of an atom
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What is an ion?
a particle where the number of electrons does not equal the number of protons
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What is an isoptope?
atoms having the same number of protons but different number of neutrons
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What is a mass number?
the number of protons plus the number of neutrons in the nucleus of an atom
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What is the mass of an electron?
1/1840 or negligible
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What is a cation?
A positive ion
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What is an anion?
A negative ion
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*1 Bromine had two naturally occurring isotopes. 79,35 Br and 81,35 Br. Give the number of protons, neutrons and electrons in each isotope.
35 - p 35 - e 44- n and 35 - p 35 - e 46 - n
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*2 State the number of protons and electrons in both Na+ and F-
Na+ - 11p 10e F- - 9p 10e
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What is an alpha particle?
A cluster of 2 protons and 2 neutrons
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Does an alpha particle have a charge?
Yes, it has a positive charge
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What is the penetrating power of an alpha particle?
Can be stopped by a piece of paper
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How does the emission of an alpha particle affect the mass and atomic number?
The mass number decreases by 4 and the atomic number decreases by 2
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What is a beta particle?
A fast moving electron
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Does a beta particle have a charge?
Yes, it is negative
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What is the penetrating power of a beta particle?
Can be stopped by a **** of thin metal for example 0.5 cm of aluminium
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How does beta emission effect the mass and atomic number of the atom?
The mass number is unchanged and the atomic number increases by 1
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What is a gamma ray?
A high energy electromagnetic radiation
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Does a gamma ray have a charge?
No, it is uncharged
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What effect does gamma ray have on the mass and atomic number of the atom?
There is no change
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What is the penetration power of gamma rays?
Can take more than 2 cm of lead to stop
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*3 Why are victims of radioactive contamination buried in lead coffins?
Radioactive emissions are stopped by a lead shield thus preventing escape of the radioactivity
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*4 Give the mass number and symbol of the isotope formed when 211 Bi decays by alpha emission
207 Ti
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What is a half-life?
The time taken for half the atoms in a radioisotope to decay or the time taken for the radioactivity of a radioisotope to fall to half of its initial value.
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Why are radio emissions dangerous?
As high energy radioactive emissions can break cell bonds within molecules causing changed in DNA causing mutation at low doses and death at high doses
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*5 Outline why radioactivity may be a health hazard.
Radiation is ionising/releases high energy/produces radicals/breaks chemical bonds/causes cell mutation. This causes burns/sickness/cancer
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*6 An isotope of iodine 131-I has a halflife of 8 days. How long would it take for 1g to be reduced to 0.125g of 131-I.
24 days
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*7 Radioactive iodine 131-I is used in medicine as a tracer. Give another use of radioactive isotopes apart from in medicine.
Carbon-14 used in radiodating/alpha emitters in smoke alarms/beta emitters to regulate the thickness of metal foil
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What radioactive isotope is used in radiotherapy for the treatment of cancer?
Cobalt-60
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What is the isotope that emits gamma rays Cobalt-60 used in?
Medicine - radiotherapy, treatment of cancer
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What is the radioactive isotope used in radio dating?
Carbon-14
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What is the radioactive isotope carbon-14 used in?
Radio-dating - calculate the age of plant and animal remains
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What is an atomic orbital?
A region in an atom that can hold up to two electrons with opposite spins
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How many electrons can a s sub shell hold?
2
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How many electrons can a p sub shell hold?
6
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How many electrons can a d sub shell hold?
10
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What shape is an s orbital?
spherical
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What shape is a p orbital?
dumbbell shape
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How are atoms clssified into the 'blocks'?
The last electron in either the s, d, p or f shell
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Define electronic configuration
The arrangement of electrons in an atom
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What two atoms have slightly different electronic configurations, both end in 4s1
Chronium and copper
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What is the filling order for electronic configuration?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s
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What is the electronic configuration of Na?
1s2, 2s2, 2p6, 3s1
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What is electron shielding or screening?
The repulsion between electrons in different shells, inner shell electrons repel outer shell electrons
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What is molar first ionisation energy of an element?
The energy required to remove one mole of electrons from one mole of its gaseous atoms
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*9 State and explain the general trend in ionisation energy. (a) across a period (b) down a group
(a) increase, because nuclear charge increases steadily but there is not much change in shielding (b) Decrease, because outer electron has increased shielding from inner electrons and it is further from the nucleus
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What three factors affect the attraction between the electrons and there nucleus?
1 - Nuclear charge; bigger the charge the bigger the attraction 2 - Electron shielding;the more sheilding the less the attraction 3 - The atomic radius;the greater the smaller the attractive force
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He has a greater ionisation energy than Ne because...
neons outer electrons has increased shielding and is further from the nucleus
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He has a greater ionisation energy than Li because...
lithiums outer electron is in a new shell which has increased sheilding and is further from the nucleus
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Ne has a greater ionisation energy than O because...
as the effect of the nuclear charge is greater but in the same sub shell so only a little extra sheliding
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Be has a greater ionisation energy than B because...
as borons outer electron is in a new sub shell so is further from the nucleus and is shielded from 2s electrons
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N has a greater ionisation energy than O because...
the electron-electron repulsion between the two paired electrons in one p oribital makes it harder to remove an electron, nitrogen has no paired electrons
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*10 Write an equation to represent the second ionisation energy of magnesium.
Mg+ (g) -> Mg2+ (g) + e-
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