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.

How will the quantity of an isotope have an effect on the avg atomic mass

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

What makes the electronegativity decrease in a group

Down a group, electronegativity decreases as electrons are held in higher orbits with more electrons overall

What makes the electronegativity decrease in a period

Across a period electronegativity decreases as valence shells approach an octet.
Losing electrons becomes less desirable as gaining electrons becomes more desirable

Atomic radius

The distance from the centre of the nucleus to the valence electrons

Atomic radius for molecular elements

Half the distance between nuclei is the atomic radius

What makes the atomic radius decrease in a group

Due to additional atomic orbits

What makes the atomic radius decrease in a period

Due to stronger attraction between the nucleus and electron cloud

How does the atomic radius vary between atomic radii, ionic radii for cations and anions

Ionic radii for cations are half the length between the nuclei atomic radius compared to atomic radii, while Ionic radii for anions are double the length between the nuclei atomic radius.

anion radii > cation radii

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

they are unstable, meaning their nuclei have excess energy and will undergo radioactive decay, emitting radiation (particles and energy) to achieve stability, whereas other isotopes are stable and do not decay, remaining unchanged over time

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

How to radioisotopes affect careers

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

Radioisotopes decay into what?

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

Decrease in atomic radius across a period.

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

What do inner electrons do

Inner electrons fully shield the nucleus for valence electrons

What do other valence electrons do

Other valence electrons partially shield the nucleus for valence electrons

What happens if you increase Z

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

Higher Zeff means stronger attraction between e- 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

What happens when you go down a group relating to ionization

Down a group, first ionization energy decreases as electrons are further away from the nucleus and are less tightly held.

What happens when you go across a period relating to ionization

Across a period, the first ionization energy increases as a full valence shell is approached.

Electron Affinity

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

Least stable and most stable where?

Most stable = highest EA

Least stable = lower EA

What does negative electron affinity mean

Negative electron affinities mean a stable anion is formed

What does positive electron affinity mean

positive electron affinities mean an unstable anion results

What happens when you go down a group relating to electron affinity

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

What happens when you go across a period relating to electron affinity

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

Difference between Ionic and Covalent bonding

Ionic:

• The result of a transfer of electrons

• Usually forms between a metal and a nonmetal

• Electrostatic in nature (+ and — attracted to eachother_

Covalent:

• The result of sharing of electrons

• Usually forms between 2 nonmetals

• The result of overlapping valence shells

What is electronegativity

• EN

• Measure of the pull an atom has on electrons

• Indirect measure, not an actual energy change like electron affinity

• Most useful as a comparision measurement

How to calculate ΔEN

• Meaning difference in electronegativity

• Calculated per bond

• Always positive

• Larger ΔEN - smaller ΔEN

What is ΔEN useful for?

A very good predictor of the nature of chemical bonds

Draw the guidelines that are used to classify bonds based on ΔEN

What do lewis dot diagrams visualize

Show valence electrons arranged around the chemical symbol.

What is another name for noble gases

Inert gases

Characteristic of noble gases

Do not react with other substances because they are already stable

Why are noble gases stable

Full valence shell

Octet rule

Elements are most stable with a valence like a noble gas with 8 electrons.

Steps to draw lewis structures of simple ionic compounds

Cations are shown as the chemical symbol with an empty valence

Anions are shown as the chemical symbol with a full valence

Both ion types must be in square brakets with the charge as the superscript

All ions must be represented, either with repeated ions or coefficients

Steps to drawing lewis structure of simple molecles

Chemical symbols represent the atom centres

A single dot represents a lone electron (unstable).unbonding e

A pair of dots represents a lone pair of electrons. unbonding e

Bonding pairs of electrons are represented with a single line between bonded atoms. bonding e

Why do covalent bonds form

• Atoms want a full octet

• Equalish sharing of e

Steps to drawing lewis structure of simple covalent compounds

• Calculate the number of valence electrons that must be represented (add up the valence electrons of all atoms).

• Identify the central atom (least electronegative, usually listed first). Draw it in the middle of the space.

• Arrange all other atoms around the central atom. Draw a single bond from each to the central atom.

• Determine how many electrons are currently represented. If all valence electrons are represented by the single bonds, the structure is done.

• If additional electrons need to be drawn in, add them to outer atoms first to give full valences/octets.

• If every outer atom has an octet but there are still valence electrons that need to be allocated, add them to the central atom.

• If there are not enough electrons to give the central atom a full valence (octet), convert a lone pair into a multiple bond with the central atom.

Advanced Lewis Structures: Electron Deficient Atoms

Exception: Group 13 elements only need 6 valence electrons.

Polyatomic ions

Groups of covalently bound atoms may overall gain or lose electrons, gaining an overall positive or negative charge.

Advanced Lewis Structures: Polyatomic Ions

For ions, subtract the charge from the electron count (account for electrons lost or gained).