Atomic Radius Trend

[Nigah Fatima]

Why is the atomic radius trend in the periodic table that atomic radius decreases across a period and increases down a group? Could someone explain why exactly that is in relation to the periodic table? I think explaining the reasoning to the trend might help me understand it instead of memorizing it.

[Tomas Burgess 3F]

Hello! The atomic radius decreases across a group because protons are being added to the nucleus, while electrons are being added to an existing electron shell (no newer shells are being added). Therefore, this causes the effective nuclear charge on the valence shell to increase, pulling the valence electrons closer to the nucleus and shortening the atomic radius.

The atomic radius increases down a group simply because more electron shells are being added, increasing shielding and overall making the atom bigger because the amount of electrons and shells being added are significantly greater than the atom above it in the group.

[Caden Ciraulo 1J]

Atomic radius decreases across a period because when this occurs, more protons and electrons are added, meaning that there is a greater force of attraction, decreasing the overall atomic radius. However, when moving down a group, the electrons are in a higher subshell, meaning that they are shielded from the protons added by the electrons that are closer. This means that as you go down a group the overall atomic radius decreases because you are moving to a higher electron shell.

[Gianna Sciole 2F]

Hi! The atomic radius decreases across a period (row) of the periodic table. This is because as you go across the periodic table, the atomic number increases by 1. This means there is another proton in the atom. The proton pulls in the electrons from the outer shell because they are positively charged and the electrons are negatively charged (and opposite charges attract).
Additionally, the atomic radius increases as you go down a group (column) of the period table. This is because the atoms get bigger because they have a new valence shell of electrons, so the radius is larger.

[Eduarda Diniz 2B]

hi! Atomic radius decreases down a period because the atomic number increases down a period, whereas the atomic radius increases down a group because the number of levels increases

[305692127]

How I like to remember it is that the atomic radius increases going down and left of the periodic table.Meanwhile the electron affinity, electronegativity, and Ionzation energy increase going from left to right and up the periodic table.

[AJackman]

Why is the atomic radius trend in the periodic table that atomic radius decreases across a period and increases down a group?
It decreases across a period because the atomic nuclei are larger and therefore more positive, drawing their electrons in tighter. It increases down a group because the electrons are moving into shells further and further from the nuclei.

[Chloe Fuson]

As you move from left to right across a period, the effective nuclear charge increases, which draws the electrons surrounding the nucleus in tighter, thus decreasing the atomic radius. However, atomic radius increases down group because a the number of shells is increasing, which means the valence shell is moving farther and farther from the nucleus, making the radius larger.

[Kayla Ziebell 1H]

Why is the atomic radius trend in the periodic table that atomic radius decreases across a period and increases down a group? Could someone explain why exactly that is in relation to the periodic table? I think explaining the reasoning to the trend might help me understand it instead of memorizing it.

So atomic radius decreases across a period because as you move across a period, one proton is added (atomic number), therefore one electron is too, thus the attraction and pull between the proton and electron is growing and pulls the molecule in tighter and makes the radius smaller. The atomic radius increases down a group because as you move down, each group gains a shell, therefore the atomic radius increases as the atom gets larger. note- as you move across a period, there are no shells being added, for elements in the same period all have the same number of shells.

[Akshat Katoch 2K]

Atomic radius decreases across a period because as you move across a period, you gain a proton and electron. This increases the nuclear charge and causes the electron to be drawn in closer, reducing the radius size. The atomic radius increases down a group because as you move down a group, you gain an electron shell and the more shells you have the further they are from the nucleus so they are not being drawn in and thus you have a bigger atomic radius.

[Rachel Bartley 2B]

As you move across a period, elements gain an electron and proton, which increases the nuclear charge within the same electron shell. This
means that the electrons have a greater nuclear charge pulling them closer to the nucleus, reducing the atomic radius as you move along a period. And as you move down a group, elements gain a new electron shell, which means the valence electrons are further from the nucleus. So with the addition of a new shell as you move down the group, the atomic radius increases.

[Mia Orr 3B]

Atomic radius decreases across a period because as there are more protons and electrons added, the electrons are pulled more towards the nucleus which makes the atomic radius smaller. Atomic radius increases down a group because electrons are filling up higher shells that are farther away from the nucleus where the attraction towards the nucleus isn't as strong.

[Colby Irvine 2A]

Like stated, effective nuclear charge means that more protons for each successive atom down a period, would increase the pulling power to the outer valence shells. As you go down a group, more energy levels are added to the valence shell, which increases atomic radius.

[Sneha Anantharaman2D]

Like everyone above said, the atomic radius decreases when going from left to right across a period because the amount of protons increases when going down a period, so the effective nuclear charge, or the pull that electrons in the outer shells feel towards the nucleus, increases. As a result, electrons are pulled in more which makes the atomic radius smaller. The radius also increases when going down a group because the amount of energy levels increases as you go down a group.

[Nathalia Garibay 1D]

I'm not quite understanding the difference between atomic and ionic radius. Can someone please explain to me the difference and in what instances they're referred to in questions?

[Benicio Rivera 1F]

Atomic radius increases going left and down. It decreases going right and up.

[Palig Kechichian 3F]

When you're going across a period, think of it in terms of electronegativity. As you move right, electronegativity increases, which means the pull towards the center of the atom will be stronger, leading to a tighter/smaller atom and atomic radius

[JafarriNocentelli 1G]

Radii decreases from right to left going down, and increases left to right going up