Chemistry Review for Final 3: Periodic Trends and Ions

Chemistry Review for Final 3: Compounds and Formulas

By William Lovering

Atoms want to have a "full" outer shell (orbital) of 8 electrons.

Hydrogen (H) and Helium (He) are the only exceptions- They have 2 in the first shell (orbital).

Atomic Radius

• One-half the distance between the nuclei of identical atoms that are bonded together.

• Measure the distance between the nuclei of two identical atoms bonded together and divide the distance by 2.

Atomic Radius

Compare the size of each atom in the picture to the right. Do you notice any trends?

Atomic Radius

• As you go across the period (row) Atomic Radius decreases.

• This is caused by an increasing positive charge in the nucleus.

• Electrons are on the same energy level going across the period, but more protons are pulling electrons in closer. This results in a smaller atomic radius.

Atomic Radius

• As you go down a group (column) Atomic Radius increases

• The number of electron shells increase as you move down the periodic table.

• This results in a larger atomic radius because the nucleus has less pull on the outer shell of electrons.

Ionization Energy

• The energy required to remove one electron from the outer shell of a neutral atom.

• This is the energy needed to form an ion.

• When ionization energy is high it is harder to remove that electron.

Ionization Energy

• Moving across a period, ionization energy increases.

• Group one has a low ionization energy and has a high reactivity

• Group 18 has a high ionization energy and are unreactive.

• Caused by an increasing positive charge in the nucleus, attracting electrons more strongly.

Ionization Energy

• decreases as you move down the periodic table.

• Elements with larger atomic radius have less pull on their electrons in the outer shell and tend to give them up.

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Electron Affinity

• The energy change that occurs when a neutral atom gains an electron.

• energy changes that are more negative have a higher electron affinity.

Electron Affinity

• As you move across the period table, electron affinities generally become more negative.

• There are some exceptions to this rule.

Electronegativity

• Measures the ability of an atom in a chemical compound to attract electrons from another atom in the compound.

• Think about what elements attract electrons.

• The highest value is 4.0 and fluorine is the most electronegative element.

Electronegativity

• Increases as you move across the periodic table.

• Group 1 and 2 metals are the least electronegative elements and tend to lose electrons when forming ions.

• Nitrogen, oxygen, and halogens are the most electronegative and strongly attract electrons when in compounds.

• Decreases or stays the same moving down a group.

Multiple Choice

Which element has the highest electronegativity?

• Potassium (K)

• Titanium (Ti)

• Bromine (Br)

• Krypton (Kr)

Multiple Choice

What is an ion?

• A Charged Atom
• A Large Atom
• A Small Atom
• A Cute Atom

Multiple Choice

Why are ions formed?

• To make our lives difficult
• Because atoms want 8 valence electrons
• Because atoms have the same number of protons and electrons
• Because atoms gained neutrons

Multiple Choice

An atom becomes _________ when it gains electrons.

• Positive
• Negative
• Neutral
• Invinsible

Multiple Choice

What is the charge of a sodium ion?

• +2

• +1

• -1

• -2

Multiple Choice

Group 17 always has ions with a charge of 

• +1
• +2
• -1
• -2

Multiple Choice

Which of the following has a -3 charge?

• Boron
• Fluorine
• Nitrogen
• Neon

Multiple Choice

Which of the following has a -1 charge? 

• Aluminum
• Bromine
• Calcium
• Potassium

Multiple Choice

Elements on the LEFT side of the periodic table will most likely form:

• Positive ions
• Negative ions
• Neutral Ions
• None of these

Multiple Choice

Cations are...

• Positive
• Negative
• Neutral
• Purring

Multiple Choice

What is the ionic symbol for a Caesium atom?

• Cs⁺
• Cs^-
• Cs⁺²
• Cs^-2

Multiple Choice

Ionization energy is the...

• energy needed to remove the outermost electron.
• ability of an atom to attract electrons from another atom.

Multiple Choice

Electronegativity is the...

• energy needed to remove the outermost electron.
• ability of an atom to attract electrons from another atom.

Multiple Choice

Which element has the smaller atomic radius: potassium (K) or bromine (Br)?

• potassium (K)
• bromine (Br)

Multiple Choice

Which element has the greatest ionization energy: Aluminum (Al)    or    Chlorine (Cl)?

• Aluminum (Al)
• Chlorine (Cl)

Multiple Choice

The Modern Periodic Table of Elements is arranged by

• atomic mass
• atomic number
• valence electrons
• number of isotopes

Multiple Choice

Which group of the periodic table is composed of inert (not reactive)  gases?

• alkali metals
• alkaline earth metals
• halogens
• noble gases

Multiple Choice

Which is an alkali metal?

• Magnesium
• Iron
• Sodium
• Europium

Multiple Choice

Which is a halogen?

• Helium
• Chlorine
• Oxygen
• Neptune

Multiple Choice

Elements in a ..................have similar chemical properties.  

• period
• group
• row

Multiple Choice

Put these elements in order of INCREASING atomic radius.

Li, O, C, F

• O, C, F, Li

• F, O, C, Li

• Li, C, O, F

• C, F, Li, O

Multiple Choice

What elements do you expect to have a high electron affinity?

• Elements that form cations

• Elements that form anions

• Transition metals

Multiple Choice

What elements have the highest Electronegativity?

• Halogens (group 17)

• Alkali Metals (Group 1)

• Alkaline-earth Metals (group 2)

• Noble gases (group 18)