五題化學選擇題不懂?

2016-02-04 2:16 pm

1. Element in the modern version of the periodic have table are arranged in order of increasing ______.
A) oxidation number
B) atomic mass
C) average atomic mass
D) atomic number

2. Atomic radius generally increases as we move _______.
A) down a group and from right to left across
B) up a group and from left to right across a period
C) down a group and from left to right across a period
D) there is no trend

3. The _____ have the most negative electron affinities
A) alkaline earth metals
B) alkali metals
C) halogens
D) transition metals

4. Element M reacts with chlorine to from a compound with the formula MCl2. Element M is more reactive than magnesium and has a smaller radius than barium. This element is ______.
A) Sr
B) K
C) Na
D) Ra

5. Na reacts with element X to from an ionic compound with the formula Na3X. Ca will react with X to form _____.
A) CaX2
B) CaX
C) Ca2X3
D) Ca3X2

回答 (1)

wanszeto

2016-02-06 5:53 pm

✔ 最佳答案

1. (D) atomic number

2. (A) down a group and from right to left across

3. (C) halogens

4. (A) Sr
Because of the formula MCl₂, M is Group II.
In Group II, Ca, Sr and Ba are more reactive than magnesium.
Among the above three Group II elements, each of Ca and Sr has a smaller radius than barium.
Hence, M may be Ca or Sr.

5. (D) Ca₃X₂
Sodium ion carries 1 positive charge.
Because of the formula Na₃X, ion of X carries 3 negative charges.
Ion of Ca carries 2 positive charges and ion of X carries 3 positive charges.
Hence, the formula is Ca₃X₂.

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