SAAT Chemistry Section 2 (Atomic Theories and Modern Periodic Table) - تحصيلي

Atom

Smallest particle of an element that retains the properties of the element

What an atom is made of

Made of a nucleus containing protons and neutrons; electrons move around the nucleus

Electron

Negatively charged particle, has very low mass and moves in high speed

Proton

Subatomic particle carrying a charge equal to but opposite that of an electron

(mass equal to 1840 of electron’s mass)

Neutron

Subatomic particle that has a mass nearly equal to that of a proton, but it carries no electric charge

Cathode ray

Originating from the cathode and traveling to the anode

Atomic number

The number of protons in an atom

Mass number

The sum of the atomic number (or number of protons) and neutrons in the nucleus

Neutrons number

Mass number - atomic number

Isotope

Atoms with the same number of protons but different number of neutrons

Isobars

Atoms of different elements similar in mass number

Atomic mass

The weighed average mass of the isotopes of that element

Visible light

Type of electromagnetic radiation which is a form of energy that exhibits wavelkie behavior as it travels through space

Speed of light

3 × 10⁸ m/s

Wavelength

Inversely proportional with frequency

The speed of light in a vacuum is equal to

The product of the wavelength and the frequency

The wavelength

The shortest distance between equivalent points on a continuous wave (presented by λ)

The speed of light is the product of

Its wavelength (λ) and its frequency (v)

White light

A small fraction of the full electromagnetic spectrum

Quanta

Matter can gain or lose energy only in small, specific amounts

Quantum

The minimum amount of energy that can be gained or lost by an atom

The energy of a quantum is given by

The product of Planck’s constant and the frequency

Planck’s constant

6.626 × 10^-32 Js

Quantum formula

E_quantum = hv

Photoelectrons

Emitted in the photoelectric effect; emitted from a metal’s surface when light of a certain frequency, or higher than a certain frequency, shines on the surface

Photon

Massless particle that carries a quantum of energy

The energy of a photon is given by the product of Planck’s constant and the frequency

E_photon = hv

H

Planck’s constant

V

Frequency

E

Photon represents energy

Wavelength and frequency are

Inversely proportional with one another

As wavelength increases,

Frequency decreases

Atomic emission spectrum of an element

The set of frequencies of the electromagnetic waves emitted by atoms of the element

Neon’s atomic emission spectrum

Consists of several individual lines of color corresponding to the frequencies of the radiation emitted by the atoms of neon

Absorption spectrum

The absorbed frequencies appear as black lines (correspond to certain frequencies absorbed by an element)

When white light passes through a prism,

It is separated into a continuous spectrum of its different components (red, orange, yellow, green, blue, indigo, and violet light)

Bohr proposed

That the hydrogen atom has only certain allowable energy states

The electron in a hydrogen atom moves around the nucleus in only certain

Allowed orbits

The smaller the electron’s orbit,

The lower the atom’s energy state, or energy level

Quantum number

‘n’ (Assigned by Bohr)

When an atom is an excited state,

The electron can drop from the higher energy orbit to a lower energy orbit

Balmer series

Set of six named spectral emission lines of the hydrogen atom, representing electron transitions from higher energy levels () down to the second energy level ()

De Broglie equation

Predicts that all moving particles have wave characteristics

Wavelength of a particle

The ratio of Planck’s constant and the product of the particle’s mass and its velocity

Heisenberg uncertainty principal

States that it is fundamentally impossible to know precisely both the velocity and position of a particle at the same time

Wave mechanical model

The atomic model in which electrons are treated as waves (quantum mechanical model)

Atomic orbital

The wave function predicts a three-dimensional region around the nucleus (describes the electron’s probable location)

Principal quantum number (n)

Defines the main energy level or electron shell of an atom, determining the size and energy of an orbital

Principal energy level

A region around an atom's nucleus where electrons reside, denoted by the principal quantum number (n)

Energy sublevels

Divisions within atomic energy levels (n=1, 2, 3...) that hold electrons in specific orbital shapes (, , , )

Atom’s electron configuration

Describes the distribution of electrons in its atomic orbitals, typically written in a sequence indicating energy levels, sublevels, and the number of electrons per subshell in superscript

Elements ground state electron configuration

Represents the most stable, lowest-energy arrangement of an atom's electrons, filled in accordance with the Aufbau principle, Pauli exclusion principle, and Hund’s rule

Aufbau principal

States that each electron occupies the lowest energy orbital available

Pauli exclusion principle

States that a maximum of two electrons can occupy a single atomic orbital, but only if the electrons have opposite spins

Hund’s rule

States that single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same orbit

Modern periodic table

Has 7 horizontal periods and 18 vertical groups and the elements are classified into alkali metals, alkaline earth metals, transition elements and non-metals, metalloids, halogens, and noble gases

Alkaline metals

Group 1 elemenets except hydrogen and its elements like sodium and lithium

Alkaline earth metals

Group 2 elemetns like magnesium and calcium

Representative elements

Group 1 and 2; they are reactive metals and an lose electrons easily

Transition elements

Group 3 til group 12 and it includes the inner transition metals like lanthanides and actinides which placed at the bottom of the periodic table

Halogens

Group 17 elements and react vigorously react with other elements like florine and chlorine

Noble gases

Group 18 elements (inert gases) are used in lamps and consider the most stable elements with least reactivity such as argon and helium

Period number

The number of the last energy orbital in the atom

Group number

Number of electrons in the last energy level

Atomic radius

Hald of the distance between two adjecent nuclei in the crystal structure of the element

When moving left to right in the period so the

Atomic radius decreases and it increases if we move down in the group

Ionization energy

The minimum energy required to remove the most loosely bound electron (valence electron) from an isolated, neutral, gaseous atom or ion

Ionization energy increases in periods when moving from left to right and decreases

In group when we go down

Electronegativity

A measure of an atom's ability to attract shared electrons in a chemical bond

Electronegativity increases in

Periods and decreases in group

When attraction increases,

Radius decreases

When radius increases,

Electronegativity increases