Chapter 1 - The Nature of Matter

Question 1

Atomic structure

Answer 1

protons = located in the nucleus, positive charge, mass of around 1
neutrons = located in the nucleus, neutral charge, mass of around 1, proton plus an electron
electrons = orbit the nucleus, negative charge, mass of around 1/1900
even though atoms are mostly empty space, electrostatic repulsion separates objects

Question 2

Standard notation

Answer 2

mass number = the sum of the number of protons and neutrons present in the nucleus of an atom
atomic number = the number of protons presents in the nucleus of an atom of a given element

Question 3

Isotopes

Answer 3

isotope = nucleus with a particular number of neutrons and number of protons
isotopes of an element differ in mass number
isotopes can be stable or unstable, but there are some stability gaps in the stable isotope zone

Question 4

Average (relative) atomic mass

Answer 4

weighted average of the masses of the stable isotopes of that element in a particular location
uses empirical data to determine value

Question 5

Atomic mass unit

Answer 5

1 atomic mass unit is defined as 1/12 of the mass of a carbon-12 atom
previously defined as the mass of a hydrogen-1 atom
the atomic mass unit was found without the knowledge of atoms through the process of electrolysis
nowadays, the atomic mass unit is found using a mass spectrometer

Question 6

Electromagnetic radiation

Answer 6

light is not a particle or a wave, but can be considered as both in different cases
thermal spectrum = continuous, all frequencies, temperature dependent
emission spectrum = discontinuous spectrum, not temperature dependent but energy dependent

Question 7

Rutherford model of the atom

Answer 7

demonstrated that accelerating charges give off light energy

however, it did not explain why electrons do not collapse into the nucleus after emitting light energy

Question 8

Bohr-Rutherford model assumptions

Answer 8

energy is proportional to the distance
electrons exist in shells at fixed distances from the nucleus
electrons cannot exist between shells
electrons can transition from one shell up to another by absorbing the correct amount of energy
electrons can transition down to lower orbits by emitting light of the correct energy as light in a single photon

Question 9

Light

Answer 9

electrons that drop down to the first orbit produce UV light
electrons that drop down to the second orbit produce visible light
electrons that drop down to the third orbit produce infrared light
in the ground state, each electron is in its lowest possible energy level
in the excited state, electrons are not always in lowest possible energy level

Question 10

Reactivity of elements

Answer 10

once an electron is moved to energy level infinity, there is nothing to stop it from moving to another atom
energy instep = movement of a valence electron to energy level infinity
no change in energy when moving to the other atom
energy outstep = movement of electron from energy level infinity back to valence shell
overall energy released is spontaneous and dissipated into the universe

Question 11

Forces of attraction

Answer 11

there are four possible forces of attraction between electrons and atoms
electrostatic attraction is the strongest

Question 12

Factors that influene force of attraction

Answer 12

difference of the number of protons (more = greater force)
difference in number of valence electrons (fewer = greater force)
difference in number of inner shells (more = lesser force)
distance from the nucleus (more = lesser force)

Question 13

Atomic radius

Answer 13

the atomic radius is half of the distance between the nuclei of two atoms of the same element
it is the balance between attraction and repulsion

Question 14

Factors that influence atomic radius

Answer 14

number of protons (more = smaller radius)
number of valence electrons (more = larger radius)
number of inner shells (more = larger radius)

Question 15

Ionization energy

Answer 15

ionization energy = energy required to remove an electron from an atom
the second ionization energy is greater than the first ionization energy because the nucleus will be pulling stronger on the electrons closer to the nucleus
the lower the ionization energy, the greater the reactivity

Question 16

How to measure ionization energy

Answer 16

shine a light through a prism and allow only one colour to enter a box filled with the gas of the element in question
keep rotating the prism until the colour entering the box has enough energy to knock the electron from the atom
the proton will then be attracted to a negatively charged plate and will will draw out electrons from from the battery, producing a current shown in the ammeter

Question 17

Factors that influence ionization energy

Answer 17

number of protons (more = greater energy)
number of valence electrons (more = lesser energy)
number of inner shells (more = lesser energy)
atomic radius (more = lesser energy)

Question 18

Electron affinity

Answer 18

electron affinity = energy lost when an electron is gained
the factors that affect electron affinity are the same as those that affect ionization energy
the greater the electron affinity, the greater the reactivity

Question 19

Electronegativity

Answer 19

a measure of the relative strength of attraction of an atom for the shared pair of electrons in a covalent bond
if two elements have different electronegativities, the one with the larger value will be the negative end of the atom, while the one with the lower value will be the positive end of the atom

Question 20

Mass spectrometer

Answer 20

the mass of the ion is determined based on the strength of the magnetic field used to make the ion produce a current
steps for determining mass =
measure magnetic field for a carbon-12 sample
measure magnetic field for the sample substance
divide the sample substance by the carbon-12 sample