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EdExcel GCSE Chemistry > Atomic Structure - Topic 1 > Flashcards

Atomic Structure - Topic 1 Flashcards

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1
Q

Describe the structure of an atom:

A

a nucleus (dense core at centre of atom) containing protons and neutrons, surrounded by electrons in shells

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2
Q

What are the two main parts of an atom?

A
  • Nucleus – very small centre
  • Electron cloud region
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3
Q

How are protons, neutrons and electrons distributed in an atom?

A

not evenly distributed

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4
Q

How are electrons in atoms arranged?

A

in energy levels (shells) that orbit the nucleus

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5
Q

How are electrons arranged on the shells of an atom?

A
  • Electrons are as far away from each other as possible on each shell as they both have a negative charge and repel
  • Electrons are paired up when spaces are taken up they can do this because they spin in opposite directions so there is an opposite quality to the 2 electrons allowing them to both be paired up despite them both having negative charges
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6
Q

Relative mass of proton:

A

1

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7
Q

Relative charge of proton:

A

+1

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8
Q

Relative mass of neutron:

A

1

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9
Q

Relative charge of neutron:

A

0

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10
Q

Relative mass of electron:

A

1/1837 or negligible

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11
Q

Relative charge of electron:

A

-1

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12
Q

Why must atoms have an equal number of protons and electrons?

A

Atoms have no electrical charge (are neutral) therefore there must be an equal number of neutrons and protons, so that the positive and negative charges balance

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13
Q

What is the size of the nucleus of an atom compared to the overall size of the atom?

A

very small

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14
Q

What do atoms of the same element have?

A

the same number of protons

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15
Q

What is the number of protons unique to and what does it determine?

A

The number of protons (atomic number) is unique to the particular element and determines what type of atom it is (element)

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16
Q

Isotopes:

A

different atoms of the same element containing the same number of protons but different numbers of neutrons in their nuclei therefore also a different mass number

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17
Q

Why is the relative atomic mass for chlorine 35.5?

A
  • It is the average mass of the isotopes present
  • A sample of chlorine contains a mixture of 75% chlorine-35 and 25% chlorine-37 and has a mass (RAM) that is the average of the masses of the isotopes (weighted according to the % of each isotope – Which isotope occurs more in nature which is why the mass is closer to 35 as it occurs more than the other isotope)
  • Chlorine therefore has a relative atomic mass (RAM) of 35.5
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18
Q

What is the atomic number?

A

(called the Proton number in physics) is the number of protons in an atom

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19
Q

Mass number =

A

protons + neutrons

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20
Q

Number of neutrons =

A

mass number (protons + neutrons) – atomic number (number of protons)

21
Q

What is the number of electrons on each shell?

A

2, 8, 8, 2

22
Q

What does the existence of isotopes result in?

A
  • The existence of isotopes results in relative atomic masses of some elements not being whole numbers
  • A sample of chlorine contains a mixture of 75% chlorine-35 and 25% chlorine-37 and has a mass (RAM) that is the average of the masses of the isotopes (weighted according to the % of each isotope – which isotope occurs more in nature which is why the mass is closer to 35 as it occurs more than the other isotope)
    • Chlorine therefore has a relative atomic mass (RAM) of 35.5
23
Q

What three particles are atoms made up of?

A

Atoms of all elements are made up of threefundamental particles:electrons,protonsandneutrons

24
Q

The structure of a particular atom can be found from two numbers that each atom has which are:

A
  • Theatomic number(called the Proton number in Physics) is the number of protons in an atom
  • Themass numberis the sum of the protons and neutrons
25
Q

What is the relative atomic mass?

A

the average mass of all isotopes of an element

26
Q

How do you calculate relative atomic mass?

A

Ar = [(relative isotopic mass 1 x %) + (relative isotopic mass 2 x %)]/100

27
Q

What is the mass number?

A

the sum of the numbers of protons and neutrons present in the nucleus of an atom

28
Q

How would an ion and an atom of an element react if they had the same number of electrons?

A

they would react similarly as they have the same number of electrons (isoelectronic)

29
Q

What was atomic theory according to Greek philosophers (before scientists)?

A
  • Before scientists, Greek philosophers pondered about the universe
  • Ancient Greeks throughout that the entire universe (or the universe they knew of at the time) was made from five elements: earth, water, air, fire and aether
  • Ancient Greeks thought that each of these “elements” had their natural place in the order of things: earth liked to be on the bottom, then water, then air, the fire, with aether floating on the very top
  • They used this idea to explain why a stone (earth) sinks in water and why fire reaches upwards in air
  • Democritus, a Greek philosopher, disagreed
  • Democritus proposed that matter could not be divided into smaller pieces forever, matter was made from small, hard particles that he called “Atoms” from a Greek word meaning “indivisible”
30
Q

What did John Dalton say about atoms and when?

A
  • In 1808 a scientist, John Dalton, stated that atoms are tiny, solid balls, like billiard bells
  • While he didn’t change the idea of the atom, he introduced the first atomic theory
31
Q

What was John Dalton’s atomic theory?

A
  1. Atoms are tiny indivisible particles
  2. Atoms of one element are all the same
  3. Atoms of different elements are different
  4. Compounds are formed by combing atoms
32
Q

What did J.J Thomson discover and when and what was he the first scientist to show?

A
  • In 1897 J.J. Thomson discovered electrons with cathode rays
  • He was the first scientist to show that the atom is made up of even smaller things
  • This knowledge changed the atomic model to the “plum pudding model”
  • Thomson thought of the electrons as raisins inside a sphere of positively charged pudding
33
Q

What did Ernest Rutherford publish and when?

A

in 1911, Ernest Rutherford published the results of his gold foil experiment (aka “Rutherford’s gold leaf experiment’)

34
Q

What was Ernest Rutherford’s gold leaf experiment in 1911?

A
  • He sent a beam of alpha particles (which were known to be positive particles) at a thin piece of gold
  • Based on the plum pudding model, the alpha particles should have gone straight through the foil, at most deflecting by fractions of a degree
  • This did not happen - most of the alpha particle did go through (as expected) however some were scattered by a few degrees (more than expected) and some actually deflected backwards
  • Years later when commenting on this experiment Rutherford said, “It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell (cannon ball) at a piece of tissue paper and it came back and hit you.”
  • Rutherford couldn’t believe the results of his experiments so her repeated them more than 100,000 times
35
Q

What did Ernest Rutherford conclude from his gold leaf experiment?

A
  1. Since most of the alpha particles went straight through, the atom was 99% atom space.
  2. Some of the alpha particles deflected back, there must be a very dense positive centre in the nucleus. He called the dense centre the “nucleus” (from a Latin word meaning “little nut”) and claimed it was made from positive particles he called “protons”.
  3. Since some of the alpha particles repelled and deflected at different angles further indicated that alpha and the centre was the same charge - positive.
36
Q

What were the flaws of Ernest Rutherford’s model of the atom?

A
  • the negatively charged electrons would be attracted to the positively charged nucleus
  • if the electrons were allowed to be anywhere on the outside of the nucleus, most of them would spiral into the centre of the atom, releasing energy as they did so
  • but atoms did not release that energy
37
Q

From thinking about the energy problems from Rutherford’s model, what did Niels Bohr propose?

A
  • Niels Bohr propose that electrons move around in specific layers or “shells”
  • in a 1913 publication he stated that every atom has a specific number of electron shells and thus the atomic model was modified once-again to put the electrons in specific locations
  • this new model is sometimes referred to as the “Bohr Model”, in honour of Niels Bohr, and sometimes called the “Rutherford-Bohr model”, to acknowledge both scientists
38
Q

What did James Chadwick discover and when?

A
  • James Chadwick performed numerous experiments and discovered neutral particle
  • In his 1932 publication, James Chadwick calls this particle the “neutron” and states that they are found in the nucleus with the protons
  • Since then, scientists have discovered that protons and neutrons are made up of even smaller things called quarks
39
Q

Provide a summary of the development of the model of the atom:

A
  • Greek Philosophers (before scientists) used five elements to explain the world (earth, water, air , fire and aether) however Democritus disagreed and said matter was made from hard particles he called “Atoms”
  • 1808 - John Dalton introduced the first atomic theory
  • 1897 - J.J. Thomson discovered electrons using cathode rays, atomic model referred to as the “plum pudding model”
  • 1911 - Ernest Rutherford’s gold foil experiment
  • 1913 - Niels Bohr proposed electrons move round the atom in shells after seeing the energy problems with Ernest Rutherford’s model
  • 1932 - James Chadwick discovered neutrons
  • Since then scientists have discovered protons and neutrons are made up of even smaller things called quarks
40
Q

Atomic nucleus:

A

Positively charged object composed of protons and neutrons at the centre of every atom with one or more electrons orbiting it in shells

41
Q

Dalton model:

A

Dalton described atoms as solid spheres, stating that different spheres made up the different elements

42
Q

Electron:

A
  • negatively charge subatomic particle which orbits the nucleus at various energy levels
  • has a negligible relative mass
43
Q

Proton:

A
  • positively charged subatomic particles present in the nucleus of the atom
  • relative has of 1
44
Q

Neutron:

A
  • neutral subatomic particle present in the nucleus of an atom
  • relative mass of 1
45
Q

Energy shell:

A

different energy levels in atoms/ions occupied by electrons

46
Q

Intermolecular forces:

A
  • the forces which exist between molecules
  • the strength of the intermolecular forces impact physical properties like boiling/melting point
47
Q

Mass number:

A

total number of protons and neutrons in the nucleus

48
Q

What do atoms of the same element have the same of?

A

atoms of a given element have the same number of protons in the nucleus - this number is unique to that element

EdExcel GCSE Chemistry (29 decks)

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