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Chemistry for the Life Sciences > Introduction to atoms > Flashcards

Introduction to atoms Flashcards

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1
Q

What are the elements with major importance to life?

A

Carbon, hydrogen, oxygen, nitrogen.

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2
Q

Why is carbon important to life?

A

It is a constituent of carbohydrates, DNA, and fat

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3
Q

Why is hydrogen important to life?

A

Constituent of body fluid, carbohydrates, protein, and fat

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4
Q

Why is oxygen important to life?

A

Used for respiration, body fluid, consituent of carbohydrates, protein, and fat

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5
Q

Why is nitrogen important to life?

A

Constituent f protein, nucleic acid, and chlorophyl.

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6
Q

What is chemistry?

A

The study of the properties and behaviour of matter

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7
Q

What is matter?

A

Matter is the physical material of the universe; it is anything that has mass and occupies space.

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8
Q

What is a property?

A

A property is any characteristic that allows us to recognsise and distinguish one type of matter from another. EG: properties could be physical (liquid) or chemical (flammability)

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9
Q

What are atoms?

A

Atoms occupy space and matter in the universe. Trillions of atoms make something up.

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10
Q

What causes the huge variety of matter in our world?

A

the variety of matter in our world is due to combinations of substances called elements.

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11
Q

What are atoms made up of?

A

Subatomic particles.

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12
Q

What charge do electrons (e-) have?

A

negative charge.

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13
Q

How do electrons move around the nucleus?

A

Electrons move around the nucleus in the outer regions forming the electronic cloud which is negatively charged.

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14
Q

What charge does a proton have?

A

a positive charge

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15
Q

What charge do neutrons have?

A

Uncharged (neutral)

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16
Q

What is the nucleus of an atom?

A

The nucleus is very small and dense and makes up 99.9% of an atoms mass. It is positively charged.

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17
Q

Mass (kg) of a proton?

A

1.67262 x 10 to the -27

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18
Q

Mass (kg) of a electron?

A

0.00091 x 10 to the -27

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19
Q

Mass (kg) of a neutron?

A

1.67493 x 10 to the -27

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20
Q

Mass (u) of proton?

A

1.0073

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21
Q

Mass (u) of neutron?

A

1.0087

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22
Q

Mass (u) of electron?

A

0.0005486

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23
Q

What is the charge number of proton?

A

+1

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24
Q

What is the charge number of neutron?

A

0

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25
Q

What is the charge number of electron?

A

-1

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26
Q

What is the overall charge of an atom?

A

Atoms as a whole are electrically neutral; they have no overall electrical charge.

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27
Q

unit of measure for atoms?

A

atomic mass unit

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28
Q

number of protons = ?

A

Number of protons = number of electrons

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29
Q

Where is the atomic number?

A

The top number

30
Q

How do you work out how many protons and electrons an atom has?

A

Atomic number (top number) tells us number of protons.
For example – Carbon has 6
We therefore know carbon also has 6 electrons since num of protons = num of electrons

31
Q

Where is atomic mass?

A

Bottom number.

32
Q

What is the atomic mass?

A

Atomic mass = number of protons + number of neutrons

33
Q

How to work out number of neutrons in an atom?

A

On the bottom is atomic mass
Atomic mass = number of protons + number of neutrons
Therefore we can work out the number of neutrons by subtracting the number of protons (atomic number) from the atomic mass.
For example, fluorine has an atomic number of 9 and an atomic mass of 19. So num of neutrons = 19-9=10. So 10 neutrons.

34
Q

The number of protons present in the nucleus is…

A

…unique to each element.

35
Q

What is an isotope?

A

Atoms of a single element that have the same number of protons and electrons but a different number of neutrons. This means that isotopes of an element have the same atomic number but a different atomic mass.

36
Q

The number of neutrons in an elements nucleus can…

A

…vary

37
Q

Isotopes can be stable or…

A

…radioactive.

38
Q

Why can the number of neutrons vary and does not have to be the same as protons or electrons?

A

Neutrons have no charge, so their number doesn’t have to be the same as protons or electrons.

39
Q

Most atoms contain…

A

Most atoms contain more neutrons than either protons or electrons.

40
Q

For some elements, the number of neutrons…

A

For some elements, the number of neutrons varies a little

41
Q

How many isotopes do elements in nature have?

A

Most elements have between 2 and 10 isotopes

42
Q

How do the properties of isotopes of an element differ?

A

Isotopes of an element have the same chemical properties (same number of electrons) but different physical properties (different mass)

43
Q

How many natural isotopes are there?

A

There are 286 isotopes which occur naturally. However, more than 2000 isotopes have been synthesised and have been used in research. These are radioactive.

44
Q

What are the abundance of isotopes?

A

The various isotopes of an element have varying abundance, but usually one is predominant.

45
Q

What are isotopes used for in biology?

A

Carbon-14 dating, nuclear magnetic resonance, radioimmunotherapy

46
Q

How do elements in nature exist?

A

Most elements in nature exist as mixtures of isotopes varying in abundance.

47
Q

What atomic mass do we use?

A

a weighted average which takes the existence of isotopes into account and their relative abundance in the environment.

48
Q

How to calculate atomic mass weighted average?

A

[Refer to powerpoint slides]

(Abundance (%) / 100) X Relative mass (amu)

49
Q

How are electrons distributed in atoms?

A
  • Electrons move around the nucleus at speeds approaching the speed of light
  • It is almost impossible to say exactly where an electron is at any specific point in time – that is the basis of the UNCERTAINTY PRINCIPAL
  • Atomic number (Z) defines the element, but it is the arrangement of electrons that determines the chemical reactivity of that element.
50
Q

What speeds do electrons move in?

A

at speeds approaching the speed of light

51
Q

What is the uncertainty principle?

A

The fact that it is almost impossible to determine where an electron is at any point in time.

52
Q

What determines the chemical reactivity of an element?

A

The arrangement of electrons

53
Q

What are electrons restrained to?

A

Electrons cannot freely circulate around the nucleus. They are restrained to specific energy levels / energy shells.

54
Q

What does it mean as energy shells increase?

A

As energy shells increase (n = 1,2,3….) they are further away from the nucleus and possess higher energy.

55
Q

What is the outermost shell of an atom known as?

A

The valence shell

56
Q

What does each energy level have?

A

Each energy level has sub levels

57
Q

What are sub levels of energy shells?

A

Locations where there is a high probability of finding electrons

58
Q

What are the sub levels known as?

A

atomic orbitals

  • These atomic orbitals have particular shapes and can hold a maximum of TWO electrons, 1 spinning clockwise, 1 spinning anti-clockwise
59
Q

What are orbitals?

A

Orbitals are the path where electrons circumnavigate the nucleus
Orbitals are not always circular (or spherical) in structure .

60
Q

Can electrons occupy the same space?

A

Electrons cannot occupy the same space – they have a negative charge so they will repel each other.

61
Q

What is the path of least resistance?

A

Energy levels and orbitals take the path of least resistance (electrons fill from the lowest energy first). This means that predictions can be made regarding an electrons location.

62
Q

Describe energy level 1 (n=1)

A

Lowest energy closest to nucleus n = 1
s-type orbital
s orbital is spherical in shape, close to and surrounding the nucleus
Called 1s (energy level 1, s-type orbital)
Maximum of 2 electrons in energy level 1 (1s)

63
Q

Describe energy level 2 (n=2)

A

Second energy level n = 2, slightly higher energy level than the first
Two types of sublevel (orbital) within n = 2:
* spherical s-type orbital: 2s
* 3 dumbbell shaped p-type orbitals: 2px 2py and 2pz
Each p-type orbital has a specific orientation along the x, y or z axis.
The three p orbitals (px , py and pz ) are considered to have identical energies. Therefore an electron will enter an empty p orbital before pairing with another electron in a half full p orbital.
Has space for 8 electrons (2 electrons in each orbital)

64
Q

Describe energy level 3 (n=3)

A
  • Third energy level n=3, slightly higher energy level than n = 2.
  • There are three types of sublevel (orbital) within n = 3 and has space for 18 electrons.
  • Spherical s-type orbital: 3s
  • 3 dumbbell shaped p-type orbitals: 3px, 3py and 3pz
  • 5 dumbbell shaped d-type orbitals: 3dxy, 3dxz, 3dyz, 3dz2 and 3dx2-y2
65
Q

Important rules governing the way electrons fill energy levels and orbitals:

A

1) Electrons fill orbits of the lowest energy level first
2) Within an energy level, electrons fill the orbitals with the lowest energy first: s orbitals represent a lower energy configuration than p orbitals and so are filled first and d orbits represent a higher energy configuration than p orbitals, so they are filled last.
3) Individual orbitals can hold a maximum of 2 electrons. When two electrons occupy the same orbital they spin in opposite directions otherwise their negative charges would force them apart.

66
Q

Why are some elements unreactive?

A

Elements are unreactive if all the outer electron orbitals are full. For example, neon is unreactive, its a noble gas with a full outer shell, so it is reluctant to lose or gain electrons with other atoms and does not take part in bonding.

67
Q

When and why do atoms react together?

A

Atoms react together to fill their outer energy levels / outer shell, allowing them to reach a more stable and unreactive state.

68
Q

What is the octet rule?

A
  • For most lighter elements, a complete and stable outer (valence) energy level requires 8 electrons.
    For example, 2 electrons in 2s + 2 electrons each in 2px, 2py, and 2pz = 8 electrons.
69
Q

What does reactivity result in?

A

Reactivity results in the formation of new bonds between atoms.

70
Q

:(

A

:)

Chemistry for the Life Sciences (12 decks)

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