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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 with atomic size. Who wants to explain how atomic size changes as we move from left to right across a period?
I think it decreases because the nuclear charge increases.
Great! Exactly. As you move left to right, the protons increase, pulling the electrons closer, which decreases the size. How about down a group?
The size increases because there are more electron shells?
That's correct! More shells mean more distance from the nucleus. To remember: 'More shells, more size!'
Next, let’s talk about metallic character. What happens to metallic character as we move left to right?
It decreases, right? Metals become less common.
Exactly! As we go right, elements become more non-metallic. Now, what happens down a group?
It increases because they can lose electrons easier?
Correct! With added shells, the outer electrons are further from the nucleus. Let's summarize: 'Left is less metal, right is more non-metal!'
How about non-metallic character? What changes do you see across a period?
It increases from left to right.
Exactly! Now about down the group?
It decreases!
Correct again! Now, how does valency vary across a period versus down a group?
It varies across and stays the same down.
Perfect! Remember: 'Valency varies with period, stays steady in the group!'
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.
Varies predictably across periods and remains constant in groups.
Size shrinks across, but grows below; metals lose their charm, as elements show!
Imagine atoms in a line, smaller ones being more refined. As you move down, they get wide; metals get bold, with no need to hide!
For atomic size, 'Smaller Right, Bigger Down' helps remember the pattern.
MNM: Metallic decreases, Non-metallic increases, Valency varies.
Term
What happens to atomic size across a period?
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Term
Metallic character trend across a period?
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Term
Non-metallic character trend down a group?
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The measure of the size of an atom, generally related to the distance between the nucleus and the outermost electrons.
The set of properties associated with metals, including the ability to lose electrons easily.
Properties of non-metals, which include a tendency to gain electrons and have high electronegativity.
The number of electrons an atom can lose, gain, or share in a chemical reaction.
The predictable pattern of changes in a specified property of elements across periods or down groups in the periodic table.
This section discusses the key trends in the modern periodic table, including atomic size, metallic character, and non-metallic character.
Trends in the modern periodic table demonstrate how properties change across periods and down groups. Key trends include a decrease in atomic size and metallic character across a period and an increase in these properties down a group. Understanding these trends is fundamental to the study of chemistry as they predict the behavior of elements.
The trends in the modern periodic table reveal how certain properties of elements change with their position in the table. This section highlights four primary trends:
Atomic Size: As you move from left to right across a period, the atomic size decreases due to the increase in nuclear charge without a corresponding increase in electron shielding. Conversely, as you go down a group, the atomic size increases because additional electron shells are added, making atoms larger.
Metallic Character: Metallic character decreases as you move across a period (left to right) because elements become less willing to lose electrons. However, as you move down a group, metallic character increases, as the additional electron shells result in weaker attraction between the nucleus and the outermost electrons, enhancing the tendency of those elements to lose electrons.
Non-metallic Character: The non-metallic character behaves oppositely to that of metallic character; it increases across a period and decreases down a group. Non-metals are more electronegative and readily gain electrons as compared to metals.
Valency: The valency of elements tends to vary predictably across a period and remains relatively constant within a group. This consistency in group alignment aids in understanding chemical bonding and reactions, making predictions about chemical behavior simpler.
These trends are crucial for students to grasp as they provide a framework for predicting the properties and behaviors of elements based on their position in the periodic table.