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A short class with Sarah and her students. The other ways are under More.
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Let's start by discussing atomic size or radius. Who can tell me what happens to atomic size as we move from left to right across a period?
I think it decreases because the elements have more protons.
That's correct! The increase in the positive charge pulls the electron cloud closer to the nucleus. And what about down a group?
The atomic size increases down a group because there are more electron shells.
Exactly! Remember this trend: 'More shells, more size.' Let's summarize: Atomic size decreases across a period and increases down a group.
Next, let’s examine metallic and non-metallic character. Who can explain how metallic character changes across a period?
It decreases as you move across a period from metals to nonmetals.
Correct! Metallic character decreases because the nonmetals become more prevalent. And what about down a group?
It increases down a group, right? More metals are found lower on the table.
Yes! For non-metallic character, it increases across a period and decreases down a group. Remember: 'Metals left, non-metals right.'
Let’s move on to ionization energy, the energy required to remove an electron. What happens to ionization energy across a period?
It increases across a period because the nucleus is stronger.
Exactly! As nuclear charge increases, it becomes harder to remove an electron. What about when going down a group?
It decreases because the outer electrons are further from the nucleus.
Absolutely! So, the trend is: Ionization energy increases across a period and decreases down a group. 'More protons mean more pull.'
Finally, let’s look at electron affinity and electronegativity. Who can explain what electron affinity is?
It's when an atom tries to gain an electron, right?
Correct! And what happens to electron affinity across a period?
It increases because the elements want electrons more.
That's right! And how does electronegativity change?
It also increases across a period and decreases down a group.
Great! Summarizing: Both electron affinity and electronegativity increase across a period and decrease down a group. 'Attractive forces are stronger rightward.'
The radius of an atom decreases across a period and increases down a group.
Decreases across a period and increases down a group.
Increases across a period and decreases down a group.
Increases across a period and decreases down a group.
Increases across a period and decreases down a group.
Atomic size shrinks and grows, to the left it shrinks, down it goes.
Imagine a tree house with different floors. The higher you go, the smaller the rooms get, but as you go lower, the rooms get larger!
MICE for trends: Metallic character Increases going down, decreases moving right; Ionization increases across, decreases down.
PINE: Properties Increase across, None down.
Term
What is the trend of atomic size across a period?
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What is ionization energy?
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How does electronegativity change down a group?
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The size of an atom, typically measured from the nucleus to the boundary of the surrounding cloud of electrons.
The tendency of an element to exhibit the properties of metals, such as conductivity and malleability.
The energy required to remove an electron from an isolated atom in its gaseous state.
The amount of energy released when an electron is added to a neutral atom to form a negative ion.
The ability of an atom to attract shared electrons in a chemical bond.
Periodicity refers to the regular trends in elemental properties across periods and groups of the periodic table.
In this section, we explore the key properties that exhibit periodicity, including atomic size, metallic character, ionization energy, electron affinity, and electronegativity, detailing how these properties change across periods and down groups in the periodic table.
Periodicity is a fundamental concept in chemistry that describes the recurring trends in various properties of elements as we move across a period or down a group in the periodic table. This section elaborates on five major properties that demonstrate periodicity:
Atomic Size (Radius): As we traverse from left to right across a period, the atomic size decreases due to the increasing positive charge in the nucleus, pulling electrons closer. However, moving down a group, the atomic size increases due to the addition of electron shells, making the atoms larger.
Metallic and Non-metallic Character: The metallic character of elements decreases from left to right across a period as elements transition from metals to nonmetals. Conversely, metallic character increases down a group. Non-metallic character behaves oppositely; it increases across a period and decreases down a group.
Ionization Energy: This is the energy required to remove an electron from an atom. Ionization energy generally increases across a period because of the increasing nuclear charge, while it decreases down a group due to the increasing distance between the nucleus and the outermost electron.
Electron Affinity: Electron affinity is the tendency of an atom to gain an electron. This property increases across a period as elements become more non-metallic and decrease down a group as larger atoms are less effective at attracting additional electrons.
Electronegativity: Electronegativity refers to the ability of an atom to attract shared electrons in a bond. It typically increases across a period and decreases down a group, following a similar trend to electron affinity.
Understanding periodicity helps predict the behavior and characteristics of elements, making it a crucial aspect of chemistry.