Quick Review Flashcards - Click to flip and test your knowledge!
Question
Who first proposed the concept of the atom in ancient Greece?
Answer
Democritus.
Question
In what year did John Dalton propose his original atomic theory?
Answer
1808.
Question
What was Dalton's postulate regarding the divisibility of atoms?
Answer
Matter consists of small, indivisible particles called atoms.
Question
According to Dalton's atomic theory, how are atoms of the same element described?
Answer
They are alike in every aspect and differ from atoms of all other elements.
Question
How does modern atomic theory contradict Dalton's postulate on the indestructibility of atoms?
Answer
Modern theory states that atoms are divisible and destructible.
Question
Which subatomic particles compose an atom according to modern theory?
Answer
Electrons, protons, and neutrons.
Question
What concept in modern atomic theory explains why atoms of the same element might have different mass numbers?
Answer
Isotopes.
Question
Which scientist discovered cathode rays in 1878?
Answer
William Crookes.
Question
At what specific gas pressure did William Crookes observe cathode rays?
Answer
$0.01 \text{ mm of Hg}$.
Question
From which part of the discharge tube are cathode rays emitted?
Answer
The negative plate (cathode).
Question
Who studied the characteristics and constituents of cathode rays in 1897?
Answer
Sir J. J. Thomson.
Question
In what direction do cathode rays travel relative to the electrodes?
Answer
In straight lines from the cathode to the anode.
Question
How do cathode rays react when exposed to a magnetic or electric field?
Answer
They are deflected, specifically being attracted towards a positively charged plate.
Question
What evidence suggested that cathode rays possess kinetic energy?
Answer
They raise the temperature of metallic objects upon which they fall.
Question
What is the mass of an electron relative to a hydrogen atom?
Answer
It is $\frac{1}{1837}$ of the mass of a hydrogen atom.
Question
What is the mass of an electron in grams?
Answer
$9.107 \times 10^{-28} \text{ g}$.
Question
What is the unit negative charge of an electron in coulombs?
Answer
$1.602 \times 10^{-19} \text{ coulombs}$.
Question
Who is credited with the discovery of protons via positive rays?
Answer
Goldstein.
Question
How can positive rays be observed travelling in the opposite direction to cathode rays in a discharge tube?
Answer
By using a perforated disc as the cathode.
Question
What is the mass of a proton compared to an electron?
Answer
A proton is 1837 times as heavy as an electron.
Question
What is the mass of a proton in grams?
Answer
$1.670 \times 10^{-24} \text{ g}$.
Question
In what year did Lord Rutherford discover the atomic nucleus?
Answer
1911.
Question
What type of particles did Rutherford direct towards the gold foil?
Answer
Alpha particles (positively charged helium atoms).
Question
What was the approximate thickness of the gold foil used in Rutherford's experiment?
Answer
One millionth of a cm.
Question
In Rutherford's experiment, what observation led to the conclusion that an atom is mostly empty space?
Answer
Most of the alpha particles went straight through the gold foil.
Question
What observation indicated a concentrated positive mass in the centre of the atom during Rutherford's scattering experiment?
Answer
Some alpha particles were deflected by large angles or bounced back.
Question
What was the major drawback of Rutherford's atomic model regarding electron stability?
Answer
It could not explain why an electron wouldn't radiate energy and collapse into the nucleus following a spiral path.
Question
According to Bohr's model, what term is used for the fixed orbits in which electrons revolve?
Answer
Energy levels (or shells).
Question
How are the various energy levels designated in Bohr's atomic model?
Answer
By the integer '$n$' (1, 2, 3...) or letters K, L, M, N...
Question
What is the formula for the energy change when an electron moves between energy states $E_{2}$ and $E_{1}$?
Answer
$E_{2} - E_{1} = h\nu$.
Question
Who discovered the neutron in 1932?
Answer
James Chadwick.
Question
What are protons and neutrons collectively called when found in the nucleus?
Answer
Nucleons.
Question
What is the approximate mass of a neutron in grams?
Answer
$1.676 \times 10^{-24} \text{ g}$.
Question
Define an element based on its atomic composition.
Answer
A pure substance made up of one kind of atoms having the same atomic number.
Question
What is the relative mass of a neutron on the $C\text{-}12$ standard scale?
Answer
1.
Question
What symbol is used to denote the Atomic Number of an element?
Answer
$Z$.
Question
How is the Atomic Number ($Z$) of a neutral atom related to its electrons?
Answer
The atomic number is equal to the number of electrons in a complete atom.
Question
What determines the value of the nuclear charge in an atom?
Answer
The atomic number of the element (number of protons).
Question
What symbol is used to denote the Mass Number of an element?
Answer
$A$.
Question
State the formula for calculating the number of neutrons ($n$) using $A$ and $Z$.
Answer
$n = A - Z$.
Question
What is the name of the shell closest to the nucleus?
Answer
K shell.
Question
What does 'electronic configuration' refer to?
Answer
The distribution of electrons in different shells or fixed orbits.
Question
According to Rule 1 of electron distribution, what is the formula for the maximum number of electrons in any shell?
Answer
$2n^{2}$.
Question
What is the maximum number of electrons the outermost shell of an atom can contain?
Answer
8.
Question
What is the maximum capacity of the penultimate shell of an atom?
Answer
18 electrons.
Question
Calculate the number of neutrons in an atom of Fluorine ($_{9}^{19}F$).
Answer
10.
Question
What is the electronic configuration of Calcium ($Z=20$)?
Answer
2, 8, 8, 2.
Question
What is the electronic configuration of Argon ($Z=18$)?
Answer
2, 8, 8.
Question
What characterizes the physical properties of isotopes of the same element?
Answer
They are different because physical constants depend on atomic mass.
Question
Name the three isotopes of Hydrogen.
Answer
Protium, Deuterium, and Tritium.
Question
What are the mass numbers of the two isotopes of Chlorine?
Answer
35 and 37.
Question
Why is the average atomic mass of Chlorine calculated as $35.5$?
Answer
Because the isotopes $^{35}Cl$ and $^{37}Cl$ exist in a ratio of $3:1$.
Question
Which noble gas is the exception to the octet rule by having only 2 electrons in its valence shell?
Answer
Helium ($He$).
Question
What is the Duplet Rule?
Answer
The tendency of an atom to achieve a stable configuration of 2 electrons in the first shell.
Question
Define an Electrovalent (Ionic) bond.
Answer
A chemical bond formed by the transfer of one or more electrons from a metallic atom to a non-metallic atom.
Question
What type of chemical bond involves the mutual sharing of electrons between two non-metallic atoms?
Answer
Covalent bond.
Question
During the formation of Sodium Chloride ($NaCl$), what ion does the Sodium atom become?
Answer
A sodium cation ($Na^{1+}$).
Question
In the formation of Calcium Oxide ($CaO$), how many electrons are transferred from Calcium to Oxygen?
Answer
Two valence electrons.
Question
What is the valency of Magnesium in Magnesium Chloride ($MgCl_{2}$)?
Answer
$+2$.
Question
How many pairs of electrons are shared in an Oxygen molecule ($O_{2}$)?
Answer
Two pairs (forming a double covalent bond).