write the mass number, atomic number,number of protons, neutrons,and electrons for He, Si, K+, N3-

I'll do two and show you how.

He. Atomic number is 2 from the periodic table, look at the periodic table and round the atomic mass to a whole number. In most cases that will give you at least one of the isotopes with that mass number. For He that will be 4. That would be written as 24He.
# protons = atomic number
# electrons = # protons
# protons + # neutrons = mass number which allows to you calculate the number of neutrons.

Si. I would go with 1428Si
# protons = 14
# electrons = 14
# neutrons = 28-14 = 14

For K^+ take away one electron.
For N^-3 add three electrons.

To find the mass number, atomic number, number of protons, neutrons, and electrons for different elements and ions, you need to understand the basic information about atomic structure and the periodic table.

1. Helium (He):
- Atomic number (Z): 2 (This is the number of protons and electrons in a neutral atom of helium.)
- Mass number (A): 4 (This is the total number of protons and neutrons in the nucleus of a helium atom.)
- Number of protons: 2
- Number of neutrons: 2 (Mass number - Atomic number = 4 - 2 = 2)
- Number of electrons: 2 (Being neutral, helium has the same number of electrons as protons.)

2. Silicon (Si):
- Atomic number (Z): 14
- Mass number (A): 28.09 (The value is often listed as an average atomic mass on the periodic table.)
- Number of protons: 14
- Number of neutrons: 14.09 (Mass number - Atomic number = 28.09 - 14 = 14.09, rounded to the nearest whole number)
- Number of electrons: 14 (In a neutral atom, the number of electrons is equal to the number of protons.)

3. Potassium ion (K+):
- Atomic number (Z): 19
- Mass number (A): Potassium has different isotopes, so the mass number can vary. One commonly occurring isotope is Potassium-39.
- Number of protons: 19
- Number of neutrons: 20 (Mass number - Atomic number = 39 - 19 = 20)
- Number of electrons: 18 (A potassium atom loses one electron to form the K+ ion, which results in a positive charge.)

4. Nitride ion (N3-):
- Atomic number (Z): 7
- Mass number (A): Nitrogen has different isotopes, so the mass number may vary. One commonly occurring isotope is Nitrogen-14.
- Number of protons: 7
- Number of neutrons: 7 (Mass number - Atomic number = 14 - 7 = 7)
- Number of electrons: 10 (A nitrogen atom gains three electrons to form the N3- ion, which results in a negative charge.)

Remember that the atomic number represents the number of protons in an atom, the mass number is the sum of protons and neutrons, and the number of electrons determines the electrical charge of an atom or ion.