An element which can exist in two or more forms in the same physical state, exhibits
isotopy
structural isomerism
allotropy
variable valency
Correct answer is C
No explanation has been provided for this answer.
-3
-2
+2
+4
Correct answer is B
No explanation has been provided for this answer.
Which of the following changes is characteristic of an alpha-particle emission?
the nucleus loses two protons and two neutrons
a proton combines with an electron giving off heat
the nucleus splits into two equal parts
four neutrons are lost
Correct answer is A
No explanation has been provided for this answer.
6C, 4Be, 7N,8 O
4Be,6 C,7 N,8 O
8O, 7 N, 6C, 4Be
7N, 8O, 6C,4Be
Correct answer is B
\(_4Be\), \(_6C\), \(_7N\), \(_8O\) is the answer because atomic size decreases across the period and increases down the group due to the effect of the positively charged nucleus./ increasing atomic numbers.
What is the mass number of an element having 20 neutrons, 15 protons and 15 electrons?
15
30
35
50
Correct answer is C
Mass number = Protons = Neutrons = 15 + 20 = 35