Year 11 Chemistry module 1.3

Periodicity

What is atomic radius?

The total distance from the center of an atom’s nucleus to the boundary of its outermost electron cloud

What is ionisation energy?

The minimum amount of energy required to remove an electron from a gaseous atom or molecule

What is first ionisation energy?

The exact amount of energy required to remove the most loosely bound electron (valence ones) from a neutral, gaseous atom to form a positive cation. It is a measure of how tightly an atom holds onto its outerm ost electron

What is electronegativity?

An atom’s abaility to attract and hold shared electrons (or electron density) toward itself when forming a chemical bond. It dicitates how atoms interact and determines the polarity of molecules.

What is reactivity?

The impulse or drive for a substance to undergo a chemical reaction, either by itself or with other materials, usually accompanied by the release of energy. Describes how easily susbtances interact chemically to form new compounds.

What are periods?

A horizontal row on the periodic table. There are 7 periods in total

What are groups?

A vertical column of elements in the periodic table. Elements in the same group have the same number of valence electrons - meaning same charges when the are ions

What are blocks on the periodic table?

S, P, D and F blocks in the periodic table that are based on which atomic orbital is being filled by an element’s valence electrons

What are metalloids?

A group of chemical elements that sit along a diagonal ‘staircase’ line seperating metals and non-metals. Elements include: Boron, silicon, germanium, arsenic, antimony, tellurium, polonium.

What is periodicity?

The recurring pattern of physical and chemical properties of elements as you move across periods and down groups in the periodic table. It occurs because elements in the same column share similar valence shell electron configurations.

What is the purpose of the periodic table?

Systemises the properties of the elements and provides a basic framework to study the periodic behaviour of physical and chemical properties of elements as well as their compounds

Which scientists made memorable contributions to the periodic table?

Johann Wolfgang Dobereiner, John Newlands, Dmitri Mendeleev, and Henry Mosely.

What did Dobereiner do for the periodic table?

Arranged then known elements in a group called triads, as each contained three elements with similar properties.

What did John Newlands do for the periodic table?

Classified 62 elements, known at the time, in increasing order of their atomic masses. Created the law of octaves.

What did Dmitri Mendeleev do for the periodic table?

Arranged elements of similar chemical properties in eight vertical columns called groups - naming the horizontal rows periods.

Started arranging the elements in ascending order of their atomic masses and found that elements having similar chemical properties appeared at regular intervals.

Left gaps in the periodic table for elements that had not yet been discovered.

What did Henry Mosely do for the periodic table>

Discovered atomic numbers, so decided to classify elements by arranging them in ascending order of their atomic numbers, rather than their masses.

What are examples of properites that vary with atomic number?

• State of matter at room temperature

• Electron configurations and atomic radii

• First ionisation energy and electronegativity

• Reactivity with water

What factors affect the periodicity trends in the periodic table?

• The number of protons in the nucleus (nuclear charge)

• The number of energy levels holding electrons (and the number of electrons in the outer energy level)

• The number of electrons held between the nucleus and its outermost electrons (called the sheilding effect). This affects the attraction between the valence electrons and the protons in the nucleus.

True or false: Metals generally possess a low melting point while non-metals generally possess high melting points

False: Metals generally possess a high melting point while most non-metals possess low melting points

Which element possesses the highest boiling point of all the elements?

Carbon

What does Pauli’s exclusion principle state?

No two electrons have the same set of four quantum numbers.

What is Pauli’s exclusion rule used for?

Determines electron configuration and orbital diagrams.

What does Hund’s rule state?

Whenever possible, electrons retain unpaired spins in degenerate orbitals

What is Hund’s rule used for?

Determines how electrons fill equal-energy orbitals in an atom

True or False: Valence electrons are responsible for most of the chemical behaviours of elements

True: They are responsible.

Elements with analogous valence electron configurations usually occur within the same group or period?

Group

Are main group elements in the s and p orbitals, the d orbitals, or the f orbitals?

s and p orbitals

Are transition metals in the s and p orbitals, the d orbitals, or the f orbitals?

d orbitals

are inner transition metals in the s and p orbitals, the d orbitals, or the f orbitals?

f orbitals

Because the physical and chemical properties of elements depend on their electron configuration, many of the physical and chemical properties of the elements tend to what?

Repeat in a pattern

Does atomic radius’ increase as periods increase or decrease?

As periods increase (Top to bottom)

Does atomic radius’ increase or decrease as groups increase?

Decrease as groups increase

Why does atomic radius increase as groups increase and as you go down the periodic table?

Increases because each successive period (row) has an additional occupied energy level

Why does atomic radius decrease across a period/as groups increase?

Decreases because the net-nuclear charge increases. It is the proton’s positive charge in the nucleus that pulls on or attracts the electrons in the orbitals

Why does the protons positive charge pull on or attracts the electrons in the orbitals?

Across a period there are more protons pulling on electrons occupying the same orbitals. The overall effect is more puling power in the same basic space. This draws the electrons in closer, making the overall atomic radius smaller at the right side of a period.

In order to remove an electron from an elements outermost shell, what must be added?

Energy

When energy is added to remove a valence electron(s) from an atom, what is created by losing the electron(s)?

An ion

What is ionisation energy?

The energy required to remove the most loosely held electron (valence electron) from a gaseous atom.

The higher the value of the ionisation energy…

The harder it is to remove valence electron(s) from the element.

Does ionisation energy increase or decrease as you go down a group (top to bottom)?

Decreases as you go down a group

Does ionisation energy increase or decrease across a period (left to right)?

Increases as you go across a period

Why does ionisation energy increase as you go across a period?

Since the atomic radius is getting smaller, the protons attract electrons from closer distance and hold them tighter.

What is electronegativity?

Describes the attraction an element has for electrons in a chemical bond.

Does electronegativity increase or decrease as you go down a group?

Decreases as you go down a group

Does electronegativity increase or decrease as you go across a period (Left to right)

Increases across a period

What is the metallic characer of an element?

How readily an atom can lose an electron

Does metallic character increase or decrease across a period (left to right)?

Increases across a period

Does metallic character increase or decrease as you move down a group?

Increases as you move down a group

Why does metallic character increase across a period?

Because the attraction between valence electrons and the nucleus is weaker, enabling an easier loss of electrons.

Why does metallic character increase as you move down a group?

Because the atomic size is increasing down a group as well. When the atomic size increases, the outer shells are farther away.

What is the principal quantum number (n)?

A value that tells us the main energy level, or shell, of an electron in an atom.

What does the principal quantum number do?

Increases down a group and average electron density moves farther from the nucleus.

What causes an increase in metallic character?

The electrons of the valence shell having less attraction to the nucleus and, as a result, can lose electrons more readily.

What causes the atomic radius to increase?

electron sheilding and the addition of more electron shells

What is electron shielding?

The way the inner-shell electrons block outer valence electrons from feeling the full positive pull of the nucleus.