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1009 available questions

Chemistry · Question 691

Why is the first ionization energy of nitrogen greater than that of oxygen?

  1. Nitrogen has a half-filled 2p subshell
  2. Nitrogen is smaller than oxygen
  3. Nitrogen has fewer electrons
  4. Nitrogen is less electronegative
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Correct answer: A

Nitrogen has a half-filled 2p subshell

Nitrogen's half-filled 2p³ subshell has extra stability; paired-electron repulsion makes an oxygen electron easier to remove.

Chemistry · Question 692

Who proposed the law of octaves?

  1. Lothar Meyer
  2. Mendeleev
  3. Newlands
  4. Döbereiner
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Correct answer: C

Newlands

John Newlands proposed the law of octaves.

Chemistry · Question 693

Mendeleev arranged elements primarily in increasing order of:

  1. Number of neutrons
  2. Atomic number
  3. Atomic mass
  4. Atomic volume
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Correct answer: C

Atomic mass

Mendeleev's table was organized mainly by increasing atomic mass, with adjustments for chemical properties.

Chemistry · Question 694

Elements in the same main-group column generally have the same number of:

  1. Total electrons
  2. Protons
  3. Valence electrons
  4. Occupied orbitals
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Correct answer: C

Valence electrons

Similar main-group chemistry results from the same number of valence electrons.

Chemistry · Question 695

Which location corresponds to the highest ionization energy and very low electron affinity?

  1. Period 1, Group 18
  2. Period 2, Group 17
  3. Period 2, Group 1
  4. Period 2, Group 2
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Correct answer: A

Period 1, Group 18

Helium in Period 1, Group 18 has the highest ionization energy and little tendency to accept an electron.

Chemistry · Question 696

In each period, the most electronegative reactive element generally belongs to:

  1. Group 1
  2. Group 17
  3. Group 2
  4. Group 16
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Correct answer: B

Group 17

The halogens in Group 17 are the most electronegative reactive elements of their periods.

Chemistry · Question 697

Which is the most electronegative element in Period 3?

  1. F
  2. P
  3. Br
  4. Cl
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Correct answer: D

Cl

Chlorine is the Group 17 element of Period 3 and is the most electronegative in that period.

Chemistry · Question 698

Which hydroxide is the most strongly basic?

  1. Mg(OH)₂
  2. Ca(OH)₂
  3. Ba(OH)₂
  4. Sr(OH)₂
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Correct answer: C

Ba(OH)₂

Group 2 hydroxides become more soluble and strongly basic down the group; barium hydroxide is strongest here.

Chemistry · Question 699

Which pair is chemically least similar?

  1. Na and K
  2. Ba and Sr
  3. Br and Cl
  4. Ca and Zn
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Correct answer: D

Ca and Zn

Calcium is an s-block alkaline-earth metal, while zinc is a d-block metal; the other pairs share a group.

Chemistry · Question 700

Which set has the strongest tendency to form positive gaseous ions?

  1. Li, Na, K
  2. Be, Mg, Ca
  3. F, Cl, Br
  4. O, S, Se
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Correct answer: A

Li, Na, K

Alkali metals have the lowest ionization energies and readily form +1 ions.