Tổng số hạt p, e, n trong nguyên tử nguyên tố X là 52. Số khối của hạt nhân nguyên tử X là
A.35.
B.32
C.39.
D.36.

Nguyên tử kali có 19 electron và 20 nơtron, vậy số khối của hạt nhân nguyên tử kali là
A.31.
B.39.
C.34.
D.30.

Ion $ { X ^ - } $ có 10e, hạt nhân có 10n. Số khối của hạt nhân nguyên tử X là
A.18
B.19
C.21
D.20

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Planting trees and using propaganda can prevent ………. .
A.Forestation
B.Reforestation
C.Deforestation
D.Underforestation

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
A good neighbor should show his ………. to those around him.
A.hope
B.will
C.generosity
D.consciousness

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
It is advisable to go to blood _____ every few months. You never know when someone might have accidents that need blood.
A.givings
B.charities
C.celebrations
D.donations

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
He cannot walk and must sit on a ………..
A.chair
B.barrow
C.wheelchair
D.wheel

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
The ………. is a place for kids and adults to meet and play sports.
A.graveyard
B.hospital
C.playground
D.church

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
People will ………. and create long lines in front of smartphone stores when a new Iphone comes out.
A.crowd
B.huddle
C.queue
D.protest

Ion $ { X ^{2-}} $ có
A.số p – số e = 2
B.số e – số n = 2
C.số e – số p = 2
D.số e – (số p + số n) = 2