Question

answer the following:

1. who proposed that atoms are indivisible and called them \atomos\?
2. which scientist discovered the electron using the cathode - ray experiment?
3. what did rutherfords gold foil experiment prove about the atom?
4. who discovered the neutron?
5. the number of protons in an atom is called the
6. write the relationship: atomic number = =
7. oxygen has an atomic number of 8 and a mass number of 16. how many neutrons does it have?
8. define cation and give one example.
9. define anion and give one example.
10. which atomic model introduced the idea of electrons revolving around the nucleus in energy levels?

problem solving

1. carbon has an atomic number of 6 and a mass number of 12. find the number of protons, electrons, and neutrons.
2. sodium (na) has 11 protons. write its electron configuration.

Explanation:

1. Democritus proposed atoms are indivisible and called them "atomos".
2. J. J. Thomson discovered the electron using the Cathode - Ray Experiment.
3. Rutherford's Gold Foil Experiment proved that the atom has a small, dense, positively - charged nucleus.
4. James Chadwick discovered the neutron.
5. The number of protons in an atom is called the atomic number.
6. Atomic Number = Number of Protons = Number of Electrons (in a neutral atom).
7. For oxygen with atomic number 8 and mass number 16, number of neutrons = Mass number - Atomic number = 16 - 8 = 8.
8. A cation is a positively - charged ion. Example: Na⁺.
9. An anion is a negatively - charged ion. Example: Cl⁻.
10. The Bohr atomic model introduced the idea of electrons revolving around the nucleus in energy levels.

For problem - solving 1:

• For carbon with atomic number 6 and mass number 12, number of protons = 6, number of electrons = 6 (since it's neutral), number of neutrons = Mass number - Atomic number = 12 - 6 = 6.

For problem - solving 2:

• Sodium (Na) with 11 protons has electron configuration 1s²2s²2p⁶3s¹.

Answer:

1. Democritus
2. J. J. Thomson
3. The atom has a small, dense, positively - charged nucleus.
4. James Chadwick
5. Atomic number
6. Number of Protons; Number of Electrons (in a neutral atom)
7. 8
8. A positively - charged ion; Na⁺
9. A negatively - charged ion; Cl⁻
10. Bohr atomic model

Problem - solving 1: Protons: 6; Electrons: 6; Neutrons: 6
Problem - solving 2: 1s²2s²2p⁶3s¹