Which of the following corresponds to an alpha particle? A. A helium nucleus, with an atomic number of 1 and an atomic
mass of 2
O B. A hydrogen nucleus, with an atomic number of 1 and an atomic
mass of 1
C. A helium nucleus, with an atomic number of 2 and an atomic
mass of 2
D. A helium nucleus, with an atomic number of 2 and an atomic mass
of 4

Atomic number=No. of protons=No. of electrons in ground state(unchanged atom)

Atomic number=13=No. of protons

Atomic mass=no. of protons+no. of neutrons=13+14=27

For isotope no. of proton=13(same atomic number but different mass number are isotopes)

no. of electrons=13

no. of neutrons=14+2=16

Explanation:

hope it's help you

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.