Loading the lesson
Loading the lesson
Search AllRounder.ai
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Learn it your way
A short class with Sarah and her students. The other ways are under More.
Sign up free to listen. Transcripts are free to read.
Today, we're going to learn about atomic radii. Who can tell me what an atomic radius is?
Is it the distance from the nucleus to the outer electrons?
Exactly right! The atomic radius measures how far the outermost electrons are from the nucleus. Can anyone guess what might happen to the atomic radius as we move across a period?
I think it decreases?
Yes! That's due to the increasing nuclear charge pulling the electrons closer. A way to remember this is by using the acronym CLOSE - Core pulling the outermost electrons with increased strength.
So, why exactly does the atomic radius decrease across a period? Student_3, any ideas?
It's because of the extra protons attracting the electrons more strongly, right?
Exactly! Each time we move to the right, we add a proton, leading to a stronger pull on those outer electrons. Can someone share a practical example?
I remember that lithium, which is smaller than sodium, is on the left of the periodic table.
Good observation! Lithium's small size compared to sodium illustrates this concept well. Let's remember with SIP - Smaller in Period.
Now let's talk about atomic radii down a group. What happens to the size?
It increases!
Correct! Each step down a group adds another electron shell. Why does that matter, Student_2?
Because those outer electrons are further from the nucleus, so they're less pulled in?
Yes! This concept can be remembered as SHIELD - Shells Help Increase Layer Distances. Well done, everyone!
As we wrap up our discussion on atomic radii, let's summarize. What happens across a period?
The atomic radius decreases!
Great! And what about down a group?
It increases!
Perfect! Remember, the keyword trends here is CLOSE for across and SHIELD for down. Let's keep these in mind for our next topic!
The distance from the nucleus to outermost electrons. It signifies the size of an atom.
Atomic radius decreases from left to right due to increased nuclear charge.
Atomic radius increases down a group due to the addition of electron shells.
To find the atomic size, watch the protons rise; from left to right it's small, down a group, it gets tall.
Imagine a tiny house (the nucleus), each time a new room (electron shell) is added, the house gets larger (increased atomic radius).
SHIELD - Shells Help Increase Layer Distances indicates why atomic radius grows down a group.
CLOSE for across a period signifying electrons are pulled Closer by Increased nuclear charge.
Term
What is atomic radius?
Click to flip
Term
What happens to atomic radius across a period?
Click to flip
Term
What happens to atomic radius down a group?
Click to flip
This section discusses the concept of atomic radius and its variation across periods and groups in the periodic table.
Atomic radius refers to the distance from the nucleus to the outermost electron in an atom. The section highlights how the atomic radius decreases across a period due to the increasing nuclear charge and increases down a group due to the addition of electron shells.
The atomic radius is defined as the distance from the nucleus of an atom to the outermost electron shell. Understanding the variation of atomic radii is essential as it influences chemical properties and behavior of elements. There are two main trends in atomic radius:
Across a Period (Left to Right): As you move across a period in the periodic table, the atomic radius decreases. This is due to the increase in nuclear charge (the number of protons in the nucleus) which pulls the valence electrons closer to the nucleus, resulting in a smaller atomic size. Each successive element in a period has an additional proton and electron, but the added electron is placed in the same shell, leading to a stronger attraction from the nucleus.
Down a Group: Conversely, as you move down a group, the atomic radius increases. This occurs because new electron shells are added with each successive element, which outweighs the increased nuclear charge. The additional shells create greater distances between the nucleus and the outermost electrons, resulting in larger atomic sizes.
These trends are pivotal in predicting how elements behave during chemical reactions and help in understanding the periodic law.