Ionic Radii

The ionic radius of an anion is always ______________ than the atomic radius of the equivalent neutral element.

• Larger

• Smaller

• Equal

Given the following chart that shows the radius of neutral elements and their corresponding ionic radii in picometers (10^-12 m), which of the following would be the best prediction for the radius of the Cl^- anion?

• The radius of Cl^- ion is GREATER than 99 pm because it has fewer e-s than neutral Cl

• The radius of Cl^- ion is LESS than 99 pm because it has fewer e-s than neutral Cl

• The radius of Cl^- ion is EQUAL to 99 pm because it has the same NUMBER of e-s as neutral Cl

• The radius of the Cl^- ion is GREATER than 99 pm because it has more e-s than neutral Cl.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

Challenge: In nerve cells, Sodium channels allow Na⁺ ions to pass easily while simultaneously blocking passage of K⁺ ions. What periodic trend is most likely the reason for this?

• Potassium's ionic radius is larger than sodium and unable to fit into the opening

• Potassium is more electronegative than sodium and binds to the channel

• Potassium's ionization energy is larger than sodium's and is rarely present as an ion in solutions.

• Potassium is a non-metal and takes on a negative charge while Sodium is a metal and takes a positive charge.

Tags

NGSS.HS-PS1-1

The sodium atom loses an electron to form a sodium ion (Na⁺). Which statement is correct with respect to its atomic radius?

• The sodium ion has a larger radius than the atom.

• The sodium ion has a smaller radius than the atom.

• The sodium ion and the sodium atom radii are the same size.

• The sodium ion has twice the radius of the sodium atom.

What happens to the ionic radii of cations compared to their neutral atoms?

• Ionic radii increase.

• Ionic radii decrease.

• Ionic radii remain the same.

• Ionic radii become zero.

Answer explanation

Ionic radii decrease when atoms lose electrons to form cations. This loss reduces electron-electron repulsion and allows the remaining electrons to be pulled closer to the nucleus, resulting in a smaller ionic radius.

Put these in increasing order of ionic radii:
Ca, Ca+, Ca+2

• Ca < Ca+ < Ca+2

• Ca+2 < Ca+ < Ca

• Ca+ < Ca+2 < Ca

Explain why the ionic radius of an anion is larger than its atomic radius.

• Due to loss of electrons

• Due to gain of electrons

• Due to increased nuclear charge

• Due to decreased electron shielding

Which of the following ions has the largest ionic radius?

Answer explanation

The ionic radius increases with negative charge and decreases with positive charge. Among the given ions, Cl^- has the largest ionic radius due to its extra electron, while Na^+, Mg^{2+}, and Al^{3+} are all cations with smaller radii.

Tags

NGSS.HS-PS1-2

Which group 2A element has the largest ionic radius?

• magnesium

• calcium

• barium

• radium

Tags

NGSS.HS-PS1-1

Which of these elements in group 1A has the largest atomic radius?

• cesium

• rubidium

• potassium

• sodium

Tags

NGSS.HS-PS1-1