Atomic radius trends

[Jordyn Lee 1J]

Hi, could someone explain the reasoning behind the trends in the periodic table for atomic radii?

[Jamie Lin 1K]

Atomic radius decreases as you go across a period because the number of proton increases, which increases the effective nuclear charge. The number of electrons also increase when going across a period, but those electrons are going into the same energy level, thus, the increase in number of protons have more effect. Atomic radius increases as you go down a group because the number of energy levels(shells) increases.

[Elizabeth Kim 2K]

Hi! Atomic radius decreases across a period and increases down a group. When moving down a group on the periodic table, there is an increase in the number of occupied principle energy levels, thus increasing the atomic radius. When moving across a period, there is a decrease in atomic radius because within a period, protons are added to the nucleus, gradually pulling electrons closer to the nucleus because of the increasing positive charge. The increasing force of attraction between the nucleus and electrons causes a decrease in atomic size. Hope this helps!

[Noa Popko 3I]

Atomic radius decreases across a row because there are more positively charged protons in the nucleus that pull the electrons in tighter.
Atomic radius increases down a column because additional shells are added.

[Ainsley DeMuth 1H]

Atomic radii increase down a group and they decrease across a period. If you travel down a specific column, the radii are going to get larger. But, if you travel horizontally to the right in a row, the radii will get smaller (due to the increasing nuclear charge pulling the electrons in tighter).

[Skylar Lo 2C]

Atomic size decrease going across a row while increases going down a column. As you move across a row, more protons are added, thus pulling in the electron cloud tighter towards the nucleus, thus reducing atomic size. Going down, more shells are added, making the size larger.

[Kurosh Zamiri 1I]

Hi! As you move across a period, the increasing amount of electrons are clumped together in the same shell, causing the protons in the nucleus to pull them closer, otherwise known as the effective nuclear charge. Therefore, across a period, atomic radius decreases. As you move down a group, the added shells contributes to a larger atomic radius. Hope this helps!

[Kurosh Zamiri 1I]

Hi! As you move across a period, the increasing amount of electrons are clumped together in the same shell, causing the protons in the nucleus to pull them closer, otherwise known as the effective nuclear charge. Therefore, across a period, atomic radius decreases. As you move down a group, the added shells contributes to a larger atomic radius. Hope this helps!

[Kurosh Zamiri 1I]

Hi! As you move across a period, the increasing amount of electrons are clumped together in the same shell, causing the protons in the nucleus to pull them closer, otherwise known as the effective nuclear charge. Therefore, across a period, atomic radius decreases. As you move down a group, the added shells contributes to a larger atomic radius. Hope this helps!

[Jessica Phung 1E]

I agree with everyone's answers above but if you still need some clarification in simpler terms, try to think about it as the pull of the proton. (which is what they're referring to as effective nuclear charge). For example, if there are more protons, obviously the electrons will be more tightly held and thus there is less space in the electron cloud. If the proton charge isn't as strong then the electrons are more loosely held. So, moving across a period, as the protons increase, the radius decreases.

[Emily Quill 2H]

Hi! The atomic radius increases the farther to the left-bottom corner you go on the periodic table because there are more shells which increase the radius and for along the period the left side has the least number of protons giving it the weaker pull on its valence electrons that are located in the same shell as those on the right side of the period, which have a stronger attraction.

[Sidharth Paparaju 3B]

Hi! As you move right in a period, the number of protons increases while the number of electron shells stays the same, so essentially Zeff gets stronger and the atom gets smaller; as you go down a column, the number of electron shells increases, so the atom gets larger.

[Kathryn Heinemeier 3H]

atomic radius will decrease across and increase going down because as you move across, there are more protons which increase the attraction within the atom, making it smaller; when going down it will increase because there are more energy levels being added which means that the radius is growing.

[Ivy Vo Dis 1C]

As you go from left to right on the periodic table, the atomic radii decreases because the number of protons in the elements increases. The positive charge of the protons will pull the electrons closer to the nucleus, decreasing atomic radii. The radius of an atom increases as you go down the periodic table because more electrons are being added on. With this, shielding by the inner electrons occurs, making the valence electrons less tightly pulled towards the nucleus.

[Mahima Manoj 1F]

Atomic radii increase down a group as additional shells are further from the nucleus. And atomic radii decrease across a period as e- are in the same shell and increasing nuclear charge pulls them in.

[Madison Yee 2B]

As you go across a period, the atomic radius decreases because the number of electrons in a subshell increases. The positive charge of the protons will pull even more on the electrons, causing the atom's radius to decrease. As you go down a group, the number of energy levels increases. As a result, there will be more electron shielding. As a result, the protons will not have as great of a pull on the electrons on the outer levels, causing the atom's radius to be larger.

[michaelcrisera]

Going across a period from left to right, the atomic radius decreases. This is because more protons are being added to the nucleus, so the effective nuclear charge is increasing. This increases the attraction between the electrons and the nucleus, pulling the outer electrons closer. Going down a group, the atomic radius increases. This is because more electrons in higher energy levels are added as you move down the column, so there are more electron "rings," extending the atomic radius.

[Ivan Huang Dis 3B]

atomic radius are also smaller for cations because they have less electrons but the same amount of protons therefore the pull on the electrons does not change. same reason why atomic radius is also larger for anions because they have gained electrons and the same number of protons.

[Acharya Ranawat 3E]

The atomic radius decreases as you go towards the top right of the periodic table. This is due to the fact that going down the periodic table has a bigger radius since the shell of the atom is bigger. Going from right to left increases the size of an atom since the effective nuclear charge is smaller since the charge of the nucleus is less, and the amount of core electrons stays the same. Hope this helps!

[Jonathan Shyu 3L]

As you go down the groups in the periodic table (horizontally), the amount of electron shells/the distance between the valence shell and the nucleus remains the same. But as you go down, you increase protons and electrons, thus increasing the attraction between the two and decreasing the atomic radius. As for going down the periods, because increasing the period means increasing the amount of electron shells, the more shells there are, the bigger they are. Thus increasing period would mean increasing atomic radius.

[Nicole Ton 3C]

Atomic radius increases as you go down a group. This is because as you go down a group, you are increasing the amount of energy levels in an atom. Each additional energy level is further away from the nucleus, so atomic radius increases as you go from top to bottom. Additionally, atomic radius decreases as you go across a period. This is because when you go across a period, the amount of energy levels stays the same, but you are adding more protons to the atom. Positively charged protons attract negatively charged electrons, so as you go across a period the atomic radius decreases since the increased attraction from the nucleus pulls the electrons in closer.