Question

question 1. the diagram below shows a periodic table with two marked arrows, one moving across a period (left to right) and the other up a group (bottom to top). label each arrow with the correct ionization energy trend. increases decreases remains constant becomes zero

Explanation:

Step1: Analyze period trend (left - right)

Ionization energy (IE) is the energy needed to remove an electron from an atom. As we move from left to right across a period (horizontal row) in the periodic table, the atomic number increases, meaning the number of protons in the nucleus increases. The electrons are added to the same valence shell. The increased nuclear charge pulls the electrons more tightly, so it becomes harder to remove an electron. Thus, IE increases from left to right across a period. The horizontal arrow (left - right) should be labeled "Increases".

Step2: Analyze group trend (bottom - top)

When moving up a group (vertical column), the number of electron shells decreases. The valence electrons are closer to the nucleus, and the nuclear charge has a stronger pull on them (with less shielding from inner electrons as the number of shells decreases). So, as we move up a group, it becomes harder to remove an electron, and IE increases. The vertical arrow (bottom - top) should be labeled "Increases". Wait, no, wait. Wait, when moving from bottom to top in a group, the atomic radius decreases, and ionization energy increases. But let's re - check. Wait, the vertical arrow is moving up a group (bottom to top). For example, in group 18 (noble gases), from Radon (bottom) to Helium (top), ionization energy increases. And in group 1, from Francium (bottom) to Hydrogen (top), ionization energy increases. And for the horizontal arrow (left to right across a period), say from Lithium to Neon, ionization energy generally increases (with some exceptions, but the overall trend is increase). So both arrows: the horizontal (left - right across period) - IE increases; the vertical (bottom - top up group) - IE increases? Wait, no, maybe I made a mistake. Wait, no, let's recall the trends:

Ionization energy trend:
- Across a period (left to right): Increases (because of increasing nuclear charge, same shell, electrons are held more tightly).
- Up a group (bottom to top): Increases (because atomic radius decreases, electrons are closer to the nucleus, held more tightly).

Wait, but the diagram: the horizontal arrow is from right to left? Wait, no, the horizontal arrow is pointing from He (right) to the left? Wait, no, the first arrow (the purple bar with the arrow) is horizontal, pointing to the left (from He towards H, Li, etc.? Wait, no, the periodic table: the first row has H and He. Then the second row Li, Be, B, C, N, O, F, Ne. Wait, the horizontal arrow: the purple bar is above the first row (H - He) and the second row? Wait, maybe the horizontal arrow is moving from right to left (from He to H, Li, etc.), which would be moving across a period in the reverse direction. Wait, that's a key mistake. Let's look at the periodic table structure. The horizontal arrow: the arrow is pointing to the left, so it's moving from right to left across a period (e.g., from He to H, or from Ne to Li, etc.). So when moving from right to left across a period, ionization energy decreases (because the reverse of the left - right increase). And the vertical arrow: moving up a group (bottom to top), ionization energy increases.

Ah, I see my mistake. The horizontal arrow is pointing to the left (so moving from right to left across a period). So across a period, left to right: IE increases; right to left: IE decreases. So the horizontal arrow (right to left across period) - IE decreases. The vertical arrow (bottom to top up group) - IE increases.

Let's re - establish:

1. Horizontal arrow (right to left across a period):
- When moving from right to left in a period, the nuclear charge decreases (since atomic number decreases), and the atomic radius increases. So it becomes easier to remove an electron, so ionization energy decreases. So the horizontal arrow (right - left across period) is labeled "Decreases".

2. Vertical arrow (bottom to top up a group):
- When moving from bottom to top in a group, the atomic radius decreases (fewer electron shells), the electrons are closer to the nucleus, and the nuclear charge has a stronger effective pull. So ionization energy increases. So the vertical arrow (bottom - top up group) is labeled "Increases".

So to label:

- Horizontal arrow (right - left across period): Decreases
- Vertical arrow (bottom - top up group): Increases

Answer:

Horizontal arrow (left - right? No, the arrow is pointing left) - Decreases; Vertical arrow (bottom - top) - Increases. So for the horizontal arrow (the one moving across the period, left - right? Wait, no, the arrow direction: the first arrow (purple bar with arrow) is pointing to the left, so it's moving from right to left across the period (e.g., from He towards H, Li, etc.). So that arrow (horizontal) - Decreases. The vertical arrow (pointing up) - Increases.

So the horizontal arrow (across period, right - left) should be labeled "Decreases", and the vertical arrow (up group, bottom - top) should be labeled "Increases".