Question

storyline 1 exam
which characteristic is not a periodic trend?
o atomic radius
o number of elements in a group
o ionization energies
o electron affinity

Explanation:

• Atomic radius: It shows periodic trends. As we move across a period (left - to - right), atomic radius generally decreases due to increased nuclear charge attracting electrons more strongly. As we move down a group, atomic radius increases because of the addition of new electron shells.
• Ionization energies: Ionization energy (the energy required to remove an electron from an atom) has a periodic trend. Across a period, ionization energy generally increases (more energy is needed to remove an electron due to increased nuclear charge). Down a group, ionization energy generally decreases (electrons are in higher - energy shells, further from the nucleus and easier to remove).
• Electron affinity: Electron affinity (the energy change when an electron is added to an atom) also has a periodic trend. Across a period, electron affinity generally becomes more negative (more favorable for electron addition in most cases). Down a group, the trend is less regular but still shows some periodic behavior.
• Number of elements in a group: The number of elements in a group (e.g., Group 1 has 6 (including Francium), Group 18 has 7 (including Oganesson)) is a fixed property of the group and does not change in a periodic (repeating) fashion based on the position of elements in the periodic table in the same way as the other properties.

Answer:

number of elements in a group