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Morgan P.
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Chemistry
TutorMe
Question:

Why does atomic radius decrease across a period and increase down a group?

Morgan P.
Answer:

Atomic radius is the distance from the edge of the atom to the center, assuming it is a perfect circle. In other words, atomic radius is the size of the atom. Electrons are arranged into shells circling the nucleus of the atom. When one shell is full of electrons, another is added farther away from the nucleus to hold extras. The amount is is electron is determined by atomic number. The nucleus contains a concentrated lump of protons, the amount also determined by atomic number. Since the protons are concentrated, they have a strong positive pull on the spread out, negatively charged electrons. Atomic radius decreases across a period and increases down a group due to Coulomb's Law. This states that the positive charge with exert a stronger attractive force on electrons that are close to it and a weaker one on those that are far away. Across a period, you gain more protons and electrons, but not more shells. The nucleus gets more concentrated positive charge and is able to exert a stronger attractive force on the shells of electrons, pulling them in closer and effectively making the atom smaller. Down a group, enough electrons are added that more shells are required. These shells are farther away from the nucleus, and though the nucleus has a stronger positive charge, it is unable to effectively pull the outer shells inward thus making the atom bigger.

Literature
TutorMe
Question:

Why does atomic radius decrease across a period and increase down a group?

Morgan P.
Answer:

Atomic radius is the distance from the edge of the atom to the center, assuming it is a perfect circle. In other words, atomic radius is the size of the atom. Electrons are arranged into shells circling the nucleus of the atom. When one shell is full of electrons, another is added farther away from the nucleus to hold extras. The amount is is electron is determined by atomic number. The nucleus contains a concentrated lump of protons, the amount also determined by atomic number. Since the protons are concentrated, they have a strong positive pull on the spread out, negatively charged electrons. Atomic radius decreases across a period and increases down a group due to Coulomb's Law. This states that the positive charge with exert a stronger attractive force on electrons that are close to it and a weaker one on those that are far away. Across a period, you gain more protons and electrons, but not more shells. The nucleus gets more concentrated positive charge and is able to exert a stronger attractive force on the shells of electrons, pulling them in closer and effectively making the atom smaller. Down a group, enough electrons are added that more shells are required. These shells are farther away from the nucleus, and though the nucleus has a stronger positive charge, it is unable to effectively pull the outer shells inward thus making the atom bigger.

ACT
TutorMe
Question:

Choose the best correction of the following sentence: Maya was shy, a introvert and quietly. a) Maya shy, an introvert and quiet. b) Maya was shy, introverted, and quiet. c) Maya was shy, introverted and quiet. d) No Change

Morgan P.
Answer:

b) is the correct answer: Maya was shy, introverted, and quiet. a) is wrong, because each adjective needs to follow the format of the one before it. 'Shy, an introvert' do not follow the same structural format. Additionally, a comma is needed before 'and'. c) is wrong because of the lack of comma before 'and' d) is wrong for lacking the comma before 'and' as well as not following the consecutive adjective format This leaves b) as the correct answer.

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