Periodic Table Trends

What did John Newlands contribute?

Discovered the Law of Octaves

What did Dmitri Mendeleev contribute?

Produced 1st periodic table w/ all known elements. Predicted properties of undiscovered elements. Grouped by similar properties and arranged by increasing atomic mass.

What did Henry Moseley contribute?

Showed atomic # should be the basis for arranging elements to eliminate discrepancies.

Periodic Law

Repeating physical and chemical properties of elements change periodically with the atomic #.

Valence Electrons

The outermost electrons in an atom.

Which electrons partake in chemical reactions?

Valence Electrons

Groups

Vertical columns on the periodic table.

What explains why similar properties appear on the periodic table?

Electron Configurations

What determines chemical properties?

The number of valence electrons.

Period

Horizontal row on the periodic table.

Electron Shielding

Valence electrons are shielded for nucleus by inner electrons.

What weakens the strength of attraction between the nucleus and valence electrons?

Electron Shielding

During electron shielding, is the repulsion between the inner and outer electrons?

Yes, the like charges cause them to repel.

What is the trend for electron shielding across a group?

Increases down a group since the energy levels are increasing.

What is the trend for electron shielding across a period?

Remains constant

Effective Nuclear Charge

The strength of attraction between protons in the nucleus and the valence electron with shielding electrons taken into account.

What is the trend for ENC across a group?

Decreases down groups; due to increase in distance and shielding electrons

What is the trend for ENC across periods?

Increases across periods; due to additional protons in the nucleus without a change in the electron shielding

Atomic Radius

Size of the atom; electrons occupy most of the volume

Why is atomic radius hard to calculate?

Electrons are located in “clouds” with no definite boundaries.

What is the trend for atomic radius across a group?

Increases down a group; due to electrons occupying additional energy levels which makes the atom bigger.

What is the trend for atomic radius across a period?

Decreases across a period; additional protons pull electrons closer making the atom smaller.

Are cations smaller or larger than their neutral atom?

smaller; due to loss of electrons

Are anions smaller or larger than their atoms?

larger; due to gain of electrons

Ionization Energy

Energy needed to remove an electron from a neutral atom or an ion.

What is the trend for ionization energy across a group?

Decreases down a group; due to # of occupied energy levels and electron shielding

What is the trend for ionization energy across a period?

Increases across a period; addition protons attract electrons.

Electronegativity

An atom’s attraction for electrons when bonded to another atom.

What element has the highest electronegativity?

Fluorine

Do elements with higher electronegativity values hold electrons closer when sharing with another?

Yes

What is the trend for electronegativity across a group?

Decreases; due to additional energy levels and electron shielding.

What is the trend for electronegativity across a period?

Increases; due to additional protons

Electron Affinity

Energy change occurring when a neutral atom attracts an electron

What is the trend for electron affinity across a group?

Decreases due to electron shielding and a decrease in effective nuclear charge.

What is the trend for electron affinity across a period?

Increases due to an increases in effective nuclear charge.

What groups are part of the main-group elements?

1, 2 and 13-18

What are some properties of metals?

Lusters, good conductors, ductile, malleable, varying melting points, form positive ions, can be mixed with other metals to form alloys

Are alloy properties different than pure metals?

Yes

Where are metals located on the periodic table?

Located to the left of the red staircase; metalloids border the red staircase

What are some properties of nonmetals?

Rarely have luster, gases are room temp., not malleable or ductile, poor conductors, exist as diatomic molecules in elemental form, form negative ions, combine w/ nonmetals to form covalent bonds

Where are nonmetals located on the periodic table?

Located to the right of the red staircase; metalloids border red staircase

Metalloids

Properties of metals and nonmetals

What are some characteristics of metalloids?

look metallic, brittle, not malleable or ductile, not good conductors

Where are metalloids found on the periodic table?

Bordering the red staircase

Which group is the alkali metals?

Group 1

How are alkaline solutions formed?

Alkali metals react with water to form alkaline solutions.

What make alkali metals very reactive?

They only have one valence electron which they want to lose.

Why are alkali metals stored in oil?

They have a high reactivity with water and oxygen in the air.

What are some characteristics of the alkali metals?

soft, easily cut, good conductors

What is the most reactive metal?

Francium

Which group is the alkaline earth metals?

Group 2

Why are alkaline earth metals highly reactive?

They have 2 valence electrons which they want to lose.

How are alkaline earth metals found in nature?

Found combined with other elements

What are some characteristics of alkaline earth metals?

harder, higher melting point than alkali metals, good conductors

Which group are the halogens?

Group 17

Which is the most reactive group of nonmetals?

Halogens

Where are Halogens found?

In sea water and rock’s of the Earth’s crust.

What is the rarest naturally occurring elements?

Astatine

How are cations formed?

A loss of electrons

How are anions formed?

A gain of electrons

What group are noble gases?

Group 18

Why do noble gases have a low reactivity?

They have a full valence shell.

Which sublevel contains the transition metals?

d-block

Do transition metals have identical or unidentical valence electron configurations?

Unidentical

What is the most common element in nature?

Hydrogen; highly reactive and unique

What orbitals do lanthanides fill?

4f orbitals

What orbitals do actinides fill?

5f orbitals

What are some properties of actinides?

unique and radioactive, unstable nuclei breaks down and releases radioactive waves

Transuranium Elements

Man-made (synthesized) elements.

Law of Octaves

When elements are arranged in increasing order of atomic mass, the 8th element resembles the 1st in physical and chemical properties.

Periodicity

Trends repeated after certain elements when the elements are arranged by atomic number

Which elements form cations?

Elements to the left of the red staircase

Which elements for anions?

Elements to the right of the red staircase.