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Physics > 1. Electical Charge And Atomic Structure > Flashcards

1. Electical Charge And Atomic Structure Flashcards

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1
Q

Electric charge

A
  • there exists a basic, smallest possible piece of charge

- 1.6x10^-19 Coulombs

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2
Q

Two types of charge quanta

A

That typified by e (negative charge)

That typified by protons (positive charge)

  • both have same magnitude
  • opposites attract, like charges repel
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3
Q

Coulomb’s law

A
  • law obeyed by interaction force between two electric charges
  • F=K Q1 Q2/ r^2
  • constant is 9x10^9 Nm^2/C^2
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4
Q

The electric field

A

If at a certain point, a tiny, stationary positive charge experiences a force of electrical origin, we say that an electric field exists at that point

E=K Q/r^2

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5
Q

Electrical potential difference

A

Potential difference (PD) acquires by a united positive charge as it is moved from point A to point B is the work done against forces of electrical origin during the process

W=F ds

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6
Q

The atomic structure of matter

A
  • all ordinary matter composed of individual entities called atoms
  • all solids, liquids, and gasses are composed of atoms
  • different types of atoms exist- each type called an element
  • elements distinguished by physical/chemical properties of atoms
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7
Q

Each atoms consists of:

A

Central core- ‘nucleus’

  • possesses most of atomic mass
  • radius 10^-14 m

Surrounding cloud of electrons

  • orbit nucleus
  • Radii 10^-10 m
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8
Q

More facts about atoms

A
  • most of an atom is empty space
  • high energy photons can penetrate atoms without collisions
  • atoms differ from one another ( number and arrangement of electrons)
  • results in differences in physical/chemical properties
  • chemical properties determined by electron structure
  • for an atoms to be electrostatically neutral, number of electrons must equal number of protons
  • atoms can easily lose or add electrons without altering nucleus-called ions
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9
Q

The nucleus

A

Composed of two functional particles:

  • protons: positivity charged (same charge as electron 1.6x10^-19 C)
  • neutrons: no charge

Atoms specified formulas:

Z^A X N

Z= atomic number (# of protons)
A= mass number (# nucleons) 
X= chemical symbol for element 
N= neutron number

A= Z+N

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10
Q

Atoms classified into what categories?

A
  1. Isotopes
  2. Isotones
  3. Isobars
  4. Isomers
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11
Q
  1. Isotopes
A
  • same number of protons, different number of neutrons
  • May be stable or unstable
  • stability depends on right mix of protons and neutrons
  • same extranuclear structure but different nuclear masses
  • if unbalanced, particle will be ejected
  • ejection is called disintegration
  • isotope is said to be radioactive
  • can not be separated chemically
  • as Z increases, number of isotopes and number of stable isotopes increases
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12
Q
  1. Isotones
A

Same number of neutrons (N) but different number of protons (Z)

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13
Q
  1. Isobars
A

Same number of neucleons(A) but different number of protons (Z)

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14
Q
  1. Isomers
A

Same number of protons (Z) as well as neutrons (N)

Identical atoms except differ in nuclear energy state

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15
Q

What are the 4 forces in nature?

A
  1. Electromagnetic
  2. Gravitational
  3. Strong nuclear
  4. Weak nuclear
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16
Q

Nuclear forces

A
  • how are protons/neutrons held together in nucleus
  • in nucleus magnetic/gravitational forces are weak
  • electrostatic force strong but repulsive
  • nuclear force responsible for binding
  • nuclear force much stronger than electrostatic
  • nuclear force is short range
  • at large distance, force on positive charges particle by nucleus is repulsive
  • as charged particle moves closer, nuclear forces dominate (attraction)
  • Neutron is neutral spring electrostatic repulsion absent
  • no region in which neutron is repelled by nucleus
  • easier to move neutron into nucleus
17
Q

Nuclear energy levels

A

Shell model of nucleus

  • assumes nucleons arranges in shells
  • shells represent discrete energy levels
  • if energy imparted, raised to excited state
  • upon returning to lower energy state, emits energy
  • sometimes energy radiated in steps
18
Q

Distribution of orbital electrons

A

Inner most orbital K shell then LMNO

Maximum number of electron in orbit is 2n^2 (n= orbit number)

K=2
L=8
M=18
N=32

19
Q

Atomic energy levels

A

Quantum mechanics:

  • e has finite probability of being anywhere in space
  • most probable location: near orbital described above
  • orbits have no real defined path-only probabilities
  • energy of atoms is a real quantity
20
Q

Electricity and magnetism

Electric fields:

A

Stationary charges particle yields a time invariant electric field

Moving charge(current) yields time varying electric field

21
Q

Magnetic fields

A

Constant current yields a time invariant magnetic field

Counter part of the electric field

Alternating current yields a time varying magnetic field

22
Q

X-rays and gamma rays- what are they?

A
  • X-rays and gamma rays are identical in nature and properties
  • electromagnetic radiation
  • time varying fields of electrical and magnetic energy
  • differ only in way in which produced
23
Q

Examples of electromagnetic radiation

A
  • radio waves
  • radar
  • visible light
  • X-rays
  • gamma rays
24
Q

Same velocity but different wavelength

A

Radio waves: 3x10^4cm
Visible light: 5x10^-5
X-rays: 1x10^-8 cm

25
Q

Ionizing radiation

A
  • used in the treatment of cancer
  • individual photon energy is large
  • individual photon have enough energy to break molecular bonds and initiate biological change
  • eg xrays, gamma rays
26
Q

Non-ionizing radiation

A
  • individual photon energy is small
  • energy is transformed into heat or mechanical energy
  • much greater quantities required to produce damage
  • eg radio waves, radar, visible light
27
Q

Difference between X-rays and gamma rays

Xrays

A

-produced extranuclearly
-Decelerating charged particle, chance of producing an X-ray
- electron passing close to nucleus
-bombard target with high energy electrons
X-ray tube (KeV) and linear accelerator(MeV energies)

28
Q

Difference between X-rays and gamma rays

Gamma rays

A
  • produced intranuclearly
  • excess energy given off as unstable nucleus decays
  • cobalt unit

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