Grade 10 Review

3 Types of radioactive emissions

Alpha particles, beta particle and gamma radiations

Atomic #

Element identify depending on the # of protons present

Average atomic mass

Weighted avg of all isopoes of a particular element in existence.

More of an isotope, it will have a greater effect on the avg atomic mass

Charge, relative mass, location and symbol of Electron

-
1/2000
Around the nucleus in ring
e-

Charge, relative mass, location and symbol of Neutron

0
1
Inside nucleus
n0

Charge, relative mass, location and symbol of Protons

+
1
inside nucleus
p+

Electronegativity

The pull an atom has on electrons
Not a direct measure - the results of ranking atoms against each other using other measures

How are the # of n,e and p in an atom

p+ = #e-

n0 = mass# - #p+

Different elements have different # of protons

How many electrons in each orbit

1st -- 2e-
2nd -- 8e-
3rd -- 8e-

How radioisotypes are diff from other isotypes

How was Mendeleev's periodic table arranged

Based on atomic mass and included gaps for elements with predicted properties that had not yet been found

How was Meyer's periodic table arranged

Based on molar volume (atomic mass / solid density)

Isotopes

Atoms of same elem type, but diff mass. (Diff # of neutrons)

Represented using a nuclear symbol/standard atomic notation or by adding a mass # to an element name or symbol with a hyphen

E.g. Carbob - 12, carbon-13 or C-12

Many careers use radioisotopes and have special safety protocols as a result

Radioisotopes ddecay into more stable atoms

Radioistopes

Isotopes w unstable nuclei.
Capable of undergoing radioactive decay in order to become more stable

Standard atomic notation

Mass # (A = P+N)
Atomic # = # of protons
Chemical symbol for elem.

Valence electrons

Outermost electrons

What do bohr-rutherford diagrams show

Complete arrangement of subatomic particles in an atom or ion: protons and neutrons in the nucleus and electrons arranged in orbits

What do valence electrons determine

Chemistr: ionic charge, molecular bonding, etc.

What is the Law of Periodicity

When elements are arranged in order of increasing atomic number, certain sets of properties recur periodically

E.g. Down a column, elements react in similar ways or atoms have similar sizes across a row

Who made the Periodic Table

Dmitri Mendeleev and Lothar Meyer

Why do ions form

Atoms are most stable with full valence shells
They will gain electrons (nonmetals) or lose electrons (metals) in order to have a stable outer orbit

Ions have diff. # of elec from atoms

What is the reason for atomic radius decrease

The decrease in atomic radius across a period is due to a phenomenon known as shielding

Shielding

Reduction of the nuclear charge experienced by an electron

Coulomb’s Law

Larger charges result in greater attraction or repulsion

A greater distance between charges results in less attraction or repulsion

Z

Atomic # Z

Zeff

Effective nuclear charge experienced by a valence electron

Inner electrons fully shield the nucleus for valence electrons

Other valence electrons partially shield the nucleus for valence electrons

Increasing Z increases # of electrons. If electrons are added to valence shell, Zeff also increases, leading to a stronger attraction between the valence and nucleus

Ionization energy

The energy required to remove the highest energy electron

The first ionization energy targets a valence electron in a neutral atom

Higher IE —> harder to remove

*always requires energy input

Down a group, first ionization energy decreases as electrons are further away from the nucleus and are less tightly held. Across a period, the first ionization energy increases as a full valence shell is approached. Higher Zeff means stronger attraction between e- and nucleus

Electron Affinity

The energy absorbed (+) or released (-) when an electron is added to an atom

Negative electron affinities mean a stable anion is formed; positive electron affinities mean an unstable anion results

Least stable and most stable where?

Most stable = highest EA

Least stable = lower EA

Down a group, electron affinity decreases as atoms have more electron.

Across a period, electron affinity increases as a full valence shell is approached.