Use the periodic table to determine the electron configuration for ca and pm in noble-gas notation
ca:
pm:
✓
ca:
[ar]4s
[ar]4s
[xe]6s2506
[xe]6s25f4

pm:
[xe6s245
[xe]6s244
[ar]3s2
[kr]452

Ca: [Ar] 4s²

Pm : [Xe} 6s² 4f⁵

Explanation:

The electronic configuation of an element in noble gas notation is written by giving the symbol of the nearest noble gas that is present in the period above it in the periodic table, followed by the electronic configuration of the remaining electrons.

For Ca the atomic no is 20

It is in 4th period.

The electronic configuration of Ca is 1s²2s²2p⁶3s²3p⁶4s²

1s²2s²2p⁶3s²3p⁶ represents the electronic congiguation of Ar with completely filled valence shell. So we can represent electronic configuration of Ca as [Ar] 4s².

The atomic no. of Promethium,Pm is 61. It's electronic configuration is

1s²2s²2p⁶3s²3p⁶4s² 3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f⁵

1s²2s²2p⁶3s²3p⁶4s² 3d¹⁰4p⁶5s²4d¹⁰5p⁶ is the configuration of the noble gas Xe . So we can represent electronic configuration of Pm as

[Xe} 6s² 4f⁵

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.