Science: Periodic Table Trends
Exploring patterns in atomic size, ionization energy, and electronegativity
Science: Periodic Table Trends
Exploring patterns in atomic size, ionization energy, and electronegativity
Science - Grade 9-12
- 1
Describe the general trend in atomic radius as you move from left to right across a period.
Think about how increasing nuclear charge affects electrons in the same shell.
Atomic radius generally decreases from left to right across a period because the number of protons increases while electrons are added to the same energy level. The stronger nuclear attraction pulls the electrons closer to the nucleus. - 2
Describe the general trend in atomic radius as you move down a group.
Atomic radius generally increases as you move down a group because each element has an additional energy level. The outer electrons are farther from the nucleus and experience more shielding. - 3
Which element has the larger atomic radius: sodium (Na) or chlorine (Cl)? Explain your answer.
Compare their positions across the same row.
Sodium has the larger atomic radius because sodium and chlorine are in the same period, and atomic radius decreases from left to right across a period. Sodium is farther to the left than chlorine. - 4
Which element has the higher first ionization energy: magnesium (Mg) or calcium (Ca)? Explain your answer.
Magnesium has the higher first ionization energy because magnesium is above calcium in the same group. Ionization energy generally decreases down a group as the valence electrons are farther from the nucleus and more shielded. - 5
State the general trend in first ionization energy across a period from left to right.
Consider how strongly the nucleus attracts outer electrons.
First ionization energy generally increases from left to right across a period because atoms hold their valence electrons more tightly as nuclear charge increases. This makes it harder to remove an electron. - 6
State the general trend in electronegativity as you move down a group.
Electronegativity generally decreases as you move down a group because the valence electrons are farther from the nucleus and more shielded. As a result, the atom attracts bonding electrons less strongly. - 7
Which element is more electronegative: fluorine (F) or oxygen (O)? Explain your answer.
Both elements are in Period 2.
Fluorine is more electronegative than oxygen because electronegativity increases from left to right across a period. Fluorine is farther to the right and attracts bonding electrons more strongly. - 8
Compare the metallic character of elements as you move from left to right across a period.
Metallic character generally decreases from left to right across a period. Elements on the left side tend to lose electrons easily, while elements on the right side are less metallic and more likely to gain electrons. - 9
Which element is more metallic: potassium (K) or bromine (Br)? Explain your answer.
Metals are generally found on the left side of the table.
Potassium is more metallic than bromine because potassium is on the far left side of the periodic table, where metals are found. Bromine is on the right side and is a nonmetal. - 10
Explain why noble gases usually have very low chemical reactivity.
Noble gases usually have very low chemical reactivity because their valence electron shells are full. A full outer shell is very stable, so these atoms do not strongly tend to gain, lose, or share electrons. - 11
Which element would have the larger atomic radius: lithium (Li) or cesium (Cs)? Explain your answer.
Look at their vertical positions in Group 1.
Cesium has the larger atomic radius because lithium and cesium are in the same group, and atomic radius increases down a group. Cesium has more energy levels, so its outer electrons are much farther from the nucleus. - 12
Which element has the higher ionization energy: neon (Ne) or argon (Ar)? Explain your answer.
Neon has the higher ionization energy because neon is above argon in the same group. Ionization energy generally decreases down a group because outer electrons are farther from the nucleus and easier to remove. - 13
An element is located in Group 17 and Period 3. Predict whether it is likely to gain or lose an electron in a chemical reaction, and explain why.
Group 17 elements are halogens.
The element is likely to gain one electron because Group 17 elements have seven valence electrons and are close to a full outer shell. Gaining one electron gives the atom a more stable electron configuration. - 14
Why do elements in the same group often have similar chemical properties?
Elements in the same group often have similar chemical properties because they have the same number of valence electrons. Valence electrons largely determine how atoms bond and react with other substances. - 15
A student claims that atomic radius and ionization energy increase in the same direction across a period. Explain why this claim is incorrect.
Compare how tightly electrons are held as you move left to right.
The claim is incorrect because across a period atomic radius generally decreases while ionization energy generally increases. As nuclear charge increases, electrons are pulled closer to the nucleus, making the atom smaller and making electrons harder to remove.