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Chemistry Unit 1 Flashcards

1
Q

Who discovered protons

A

Ernest rutherford

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2
Q

How did Rutherford discover protons

A

By striking lighter elements such as nitrogen by alpha particles

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3
Q

A proton has a mass , which is about _____times the mass of
electrons.

A

1840

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4
Q

What is atomic number

A

The atomic number (Z) of an element equals the number of protons in the nucleus of each of its atoms.

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5
Q

What is mass number

A

The total number of protons and neutrons in the nucleus of an atom is its mass number (A)

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6
Q

What are isotopes

A

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons

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7
Q

Who proposed that light consists of electromagnetic waves

A

James clerk maxwell

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8
Q

_______________ is the emission and transmission of energy in the form of electromagnetic waves.

A

Electromagnetic radiation

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9
Q

List electromagnetic waves three primary characteristics

A

-wavelength
-frequency
-speed

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10
Q

What is wavelength?

A

Wavelength (λ, Greek lambda), is distance the wave travel during one cycle .It is expressed in meters (m) and often, for very short wavelengths, in nanometers (nm), picometers (pm), or angstrom (Å).

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11
Q

What is frequency

A

is the number of cycles the wave undergoes per second

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12
Q

The speed of a wave depends on

A

It depends on the type of wave and the nature of the medium through which it is traveling

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13
Q

What was max Planck’s revolutionary proposal

A

energy like matter is discontinuous

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14
Q

The energy of these small packets of energy is given by

A

E=hv
H=planks constant which is 6.63 times 10 to the power of -34
V=frequency

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15
Q

atoms and molecules could emit or absorb energy only in discrete quantities, like small packages or bundles. Each of these small “packets” of energy are called

A

Quantum or photon

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16
Q

Energy is always emmited or absorbed in internal multiples of?

A

Hv

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17
Q

What is the photoelectric effect?

A

is a phenomenon in which electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum frequency,

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18
Q

What is threshold frequency

A

It’s the minimum frequency needed to eject electrons from the surface of a metal

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19
Q

Plato and Aristotle believed atoms were?while democratus believed?

A

-They believed atoms were continuous
-democratus believed that atoms were discrete

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20
Q

What does atoms or atomos mean?

A

It means indivisible

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21
Q

What was democratus’s ideas based on?

A

Philosophical speculation rather than experimental evidence

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22
Q

The laws that are the basis for daltons atomic theory are?

A

-the law of conservation of mass
-the law of definite proportion

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23
Q

Modern atomic theory is generally said to begin with

A

John Dalton

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24
Q

Dalton’s work was mainly about

A

– how they combine to form new compounds – rather than about the internal structure of atoms.

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25
Modern theories about the physical structure of atoms begined when
J.J. Thomson discovered the electron in 1897
26
Explain jj Thomson cathode ray experiment
The cathode ray experiment, famously conducted by J.J. Thomson in the late 19th century, involved passing electric current through a vacuum tube containing gas at low pressure. When a high voltage was applied, a beam of particles (later identified as electrons) was emitted from the cathode and traveled towards the anode. Thomson observed that the cathode rays could be deflected by electric and magnetic fields, indicating that they carried a negative charge. By measuring the degree of deflection, he was able to calculate the charge-to-mass ratio of the particles.
27
Who found the mass of an electron
Robert A. Millikan measured the charge of the electron by measuring the effect of an electrical field on the rate at which charged oil drops fell under the influence of gravity. Based on careful experiments, Millikan established the charge on an electron as e = –1.602 × 10–19 C. He used this value and Thomson’s mass/charge ratio to calculate an electron’s mass to be 9.109 × 10–31 kg.this experiment is called the oil drop experiment
28
_________________is the spontaneous emission of particles and/or radiation from the unstable nuclei of certain atoms such as uranium, radium, etc
Radioactivity
29
List the three radioactive rays
-alpha ray -beta ray -gamma ray
30
What are alpha rays?
They consist of positively charged particles, called α particles. They have a mass of about four times that of a hydrogen atom and a charge twice the magnitude of an electron and they are also identical to helium nuclei(He2+).
31
What are beta rays
Are negetively charged rays
32
What are Gamma rays
Gamma rays are rays that have no charge
33
What model of an atom did jj Thomson propose
The plum pudding model
34
Who conducted the gold foil experiment and what kind of impact did this experiment have?
-Ernest Rutherford -it showed that there is plenty of space in an atom which showed that the plum pudding model was not correct
35
Who discovered the neutrons and how?
-James Chadwick He hit beryllium metal with alpha rays which obtained a strong penetrating radiation from the metal this radiation consists of neutrons
36
How did Rutherford discover protons?
By striking lighter elements like nitrogen with alpha particles
37
In a vacuum, electromagnetic waves travel at ?
3 × 10^8 m/s, which is a physical constant called the speed of light
38
EMR comes in a broad range of frequencies called
the electromagnetic spectrum
39
What happens when the frequency is less than or past the threshold frequency
When it’s the less than the threshold frequency it can’t remove an electron When it’s past the threshold frequency the excess energy is given as kinetic energy
40
What is intensity of light
It’s the measure of the number of photons present in a given part of a beam. A greater intensity means that more photons are available to release electrons
41
What is the dual nature of light?
Light has particle like and wave like behaviour
42
The dual nature of light is proven by
-it’s particle like behaviour By the photoelectric effect -it’s wave like behaviour By the double slit experiment
43
______________are produced from the emission of photons of electromagnetic radiation
Atomic or line spectral
44
What did Niels Bohr (a Danish physicist) explain
why the orbiting electron does not radiate energy as it moves around the nucleus.
45
Bohr used __________ and ____________ idea to form assumptions
Planks and Einstein
46
List the assumptions of Niels Bohr
1. The electron in hydrogen atom travels around the nucleus in a circular orbit. 2. The energy of the electron in atom is proportional to its distance from the nucleus. The further electron is from the nucleus; the more energy it has. 3. Only limited number of orbits with certain energies are allowed. This means, the orbits are quantized. 4. The only orbits that are allowed are those for which the angular momentum of the electron is an integral multiple of h/2π. 5. As long as an electron stays in a given orbital, it neither gain or loss energy. That means, the atom does not change its energy while the electron moves within an orbit. 6. The electron moves to higher energy orbit only by absorbing and emit energy in the form of light when it falls to a lower energy orbit. The energy (photon) of the light absorbed or emitted is exactly equal to the difference between the energies of the two orbits.
47
What is the quantum condition
the angular momentum, mvr, of the electron can take only certain permitted values and it’s an integral multiple of h/2π. This requirement is called quantum condition.
48
True or false: only permitted values of the radii of the electron path in the hydrogen atom are those proportional to the square of a whole number, n
True
49
How can we calculate the energy by using the energy level of an electron
E= -Rh\n2 Rh = 2.18 times 10 to the power of -18
50
The most stable energy state is
N=1 The ground state or ground level
51
N=2,3…… are called
The excited state or excited level
52
How can we calculate change in E
= -Rh (1/nf2 -1/ni2)
53
The Lyman series is
Nf= 1 and it’s found in the ultraviolet
54
What is the balmer
Nf = 2 visible and ultra violet
55
What is the paschen series
Nf=3 and it’s Infrared
56
The Brackett series is
Nf= 4 and infrared
57
The larger the electron drops ( larger orbit radius) what happens to the energy
The greater the energy- higher frequency and shorter wavelength of the emitted photon
58
What are some limitations of Bohr model
—it doesn’t explain the atomic spectra of more complicated atoms even that of helium , the next simplest element It doesn't explain about further splitting of spectral lines in the hydrogen spectra on application of a magnetic field. —It considers electrons to have both known radius and orbit, which is impossible according to Heisenberg's uncertainly principle.
59
What did de broglie reason
He reasoned that if electrons have wavelike motion and are restricted to orbits of fixed radii that would explain why they have only certain possible frequencies and energies.
60
What equation did de broglie derive and how
Wavelength =h/mv He derived it by combining Einstein and planks equation
61
What does quantum mechanics study about and what are its two central concepts
It studies about the electronic structure( how electrons are arranged about the nucleus in the atom) -the uncertainty principle and the wave behaviour of matter
62
Hat is the formula of the Heinberg principle
(∆x)(∆p)≥ h/4π or (∆x)(∆mv)≥ h /4π

Chemistry (4 decks)

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