Atomic Radius Trends in The Periodic Table of Elements
The atomic radius is the distance of the outermost electron to the atomic nucleus and indicates the size of an atom. The further to the right the number of protons and neutrons increases so that the attractive force of the nucleus to the outermost electrons is stronger so that the atomic radius becomes smaller.
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LearningTranscript
00:00Atomic radius is the distance from the nucleus to the outermost shell.
00:07Look at the following illustration.
00:10This is the nucleus,
00:16and this is the electron.
00:22In simple terms, the electron path is in the form of a spherical shell in a three-dimensional view.
00:29Well, the distance between the nucleus and the surface of the ball is the atomic radius.
00:35This concept seems understandable.
00:42Now, we will analyze the trend of atomic radii for elements in a certain period or group.
00:51We start from elements that are in the same group.
00:57In this modern periodic table, the same group contains elements from several periods.
01:04This means that each element in the same group has a different period.
01:12Previously we knew that the placement of elements in a certain period was based on the number of shells.
01:18Elements in period 1 have one shell.
01:23Elements in period 2 have two shells.
01:28Elements in period 3 have three shells.
01:31And so on.
01:39Well, the more shells, the further the distance of the outermost shell from the nucleon.
01:48This means that the larger the period, the greater the radius value.
01:54In atoms of the same group, from top to bottom the atomic radius increases.
02:02Now, we will analyze elements that are in the same period.
02:08The same period contains several elements from various groups.
02:14This means that each element in the same period has a different group.
02:22We know that in the same period, the number of atomic shells is the same.
02:27However, in different groups, the number of outer electrons is different.
02:35Let's take three atoms as an illustration.
02:49Since the electrons in the shells other than the outermost shell are the same,
02:53we can ignore the effects of the electrons in this shell.
02:58The main focus of the study is only the electrons in the outermost shell.
03:05Electrons are negatively charged particles.
03:09Protons are positively charged particles.
03:13There is an attractive force between particles with different charges.
03:17The direction of the Coulomb force is from the electrons to the atomic nucleus.
03:22This force works on every atom.
03:26If we still remember the concept of the resultant force,
03:31several forces acting on the same object have a resultant force.
03:38What is meant by the object here is the path of the electron.
03:44At all times the direction of the force is the same.
03:47The direction is towards the atomic nucleus.
03:50This force is the centripetal force.
03:56If one electron exerts a force of F,
04:01the resultant centripetal force of atom 1 is F.
04:05The other atoms are 2F and 3F.
04:11The exact same path gets a different force, automatically the response is different.
04:16The path that gets the greater force will be attracted to the atomic nucleus more strongly than the others.
04:22What does that mean?
04:26This means that the more electrons in the outermost shell,
04:29the distance of the last shell to the axis will decrease.
04:35In other words, in the same period, the atomic radius from left to right will decrease.
04:44When combined with the periodic table of elements,
04:48the direction of increasing atomic radius is from right to left and from top to bottom.
04:55Elements in the lower left corner tend to have the largest atomic radii.
05:02Thank you for following this channel.