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Questions and Answers
Who is credited with arranging elements by atomic number?
Who is credited with arranging elements by atomic number?
What happens to the atomic radius when moving down a group in the periodic table?
What happens to the atomic radius when moving down a group in the periodic table?
What is the result of an increased positive charge in the nucleus when moving from left to right across a period?
What is the result of an increased positive charge in the nucleus when moving from left to right across a period?
Who is credited with grouping elements into metals, non-metals, and semimetals?
Who is credited with grouping elements into metals, non-metals, and semimetals?
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What is observed when arranging elements by atomic mass?
What is observed when arranging elements by atomic mass?
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What is the result of an increase in electron shells when moving down a group?
What is the result of an increase in electron shells when moving down a group?
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Which direction across a period in the periodic table do reactivity trends for metals increase?
Which direction across a period in the periodic table do reactivity trends for metals increase?
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What is the reason for the increase in reactivity of metals down a group?
What is the reason for the increase in reactivity of metals down a group?
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What is the characteristic of metals that makes them good conductors of heat and electricity?
What is the characteristic of metals that makes them good conductors of heat and electricity?
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What is the primary factor that determines the rate of reaction according to the collision theory?
What is the primary factor that determines the rate of reaction according to the collision theory?
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Which of the following is a characteristic of nonmetals?
Which of the following is a characteristic of nonmetals?
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What is the property of semimetals that is intermediate between metals and nonmetals?
What is the property of semimetals that is intermediate between metals and nonmetals?
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Study Notes
Contributions of Scientists
- Johann Dobereiner discovered triads of elements with chemical similarities.
- John Newlands arranged elements by atomic mass and observed periodic trends and families of elements.
- Dmitri Mendeleev grouped elements by physical properties, observed periodic trends and similarities in grouping, and made predictions for yet to be discovered elements.
- Henry Moseley arranged elements by atomic number.
- Antonine Lavoisier grouped elements into metals, non-metals, and semimetals.
The Structure of the Periodic Table
- Atomic radius increases down a group and from right to left across a period.
- When moving down a group, the number of electron shells increases, causing the outermost electrons to be farther from the nucleus, increasing the width of the atom.
- When moving from left to right across a period, the number of protons increases, resulting in a stronger positive charge in the nucleus, which pulls the outermost electrons in, making the atom smaller.
Reactivity Trends for Metals
- Metals are located in the bottom left of the periodic table.
- Reactivity of metals increases down a group due to a greater atomic radius, which leads to a weaker attraction between outermost electrons and the nucleus.
- A weaker attraction means less energy is required to remove the outermost electron to initiate chemical bonding or a reaction.
Element Notation
- Atomic number (Z) = number of protons = number of electrons.
- Mass number (A) = number of nucleons = number of protons + number of neutrons.
Properties of Metals, Nonmetals, and Semimetals
- Metals: solid at room temperature (exception: mercury), malleable, ductile, good conductor of heat and electricity, lustrous, high density, high boiling and melting points.
- Nonmetals: can be a gas, liquid, or solid (mostly gases), high ionisation, high electronegativity, poor thermal conductors, poor electrical conductors, little or no metallic lustre, low melting and boiling points.
- Semimetals: form solid at room temperature, malleable, ductile, average thermal conductivity, semi-conductive, brittle.
Drivers of Reactions
- The rate of reaction is the speed at which a chemical reaction occurs.
- Collision Theory: a chemical reaction can only occur if reacting particles collide at the correct orientation with sufficient energy (activation energy).
- The kinetic theory of matter: all matter is composed of particles that are in constant motion.
Factors Affecting the Rate of Reaction
- Temperature: increases kinetic energy, particles move faster, increasing the frequency of collisions, and thus the rate of reaction.
- (Note: other factors, such as concentration, surface area, and catalysts, can also affect the rate of reaction.)
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Description
Identify the contributions of famous scientists to the development of the periodic table, including Johann Dobereiner, John Newlands, Dmitri Mendeleev, Henry Moseley, and Antonine Lavoisier. Test your knowledge of their discoveries and how they shaped our understanding of the elements.
