Grade 10 chemisty – The Atom Structure of the atom Quiz
1. Which particles are found in the nucleus of an atom?
The nucleus contains positively charged protons and neutral neutrons; electrons orbit the nucleus.
2. What does the atomic number of an element represent?
Atomic number equals the number of protons and defines the element (for example, oxygen has atomic number 8).
3. What is the mass number of an atom?
Mass number (A) is protons + neutrons; electrons have negligible mass and are not included.
4. Chlorine has atomic number 17 and mass number 35. How many neutrons does one chlorine atom have?
Neutrons = mass number − atomic number = 35 − 17 = 18.
5. A neutral sodium atom has atomic number 11. How many electrons does it have?
A neutral atom has equal numbers of protons and electrons; sodium has 11 protons so 11 electrons.
6. What type of ion is formed when an atom loses one or more electrons?
Loss of electrons leaves more protons than electrons, giving a net positive charge (cation).
7. Which statement best describes isotopes of the same element?
Isotopes are atoms of the same element (same Z) with different mass numbers due to differing neutrons.
8. According to the Bohr model, where are electrons found?
Bohr proposed electrons occupy discrete energy levels (shells); they can jump between levels by absorbing or emitting energy.
9. What is the maximum number of electrons that can occupy the third shell (n = 3)?
The third shell can hold up to 2n^2 = 2×3^2 = 18 electrons (though for lighter elements it often contains up to 8).
10. How many valence electrons does an oxygen atom have? (O, atomic number 8)
Oxygen's electronic configuration is 2,6 so it has 6 electrons in the outermost shell (valence electrons).
11. What is the charge of the ion formed when magnesium (Mg) loses two electrons?
Mg has 12 protons; losing two electrons leaves it with two more protons than electrons, giving a +2 charge (Mg2+).
12. Which scientist’s model concluded that most of the atom’s mass is in a small dense nucleus?
Rutherford's gold foil experiment showed alpha particles scattering from a small dense nucleus, leading to his nuclear model.
13. Who proposed that atoms are indivisible solid spheres as the earliest atomic model?
Dalton suggested atoms were tiny indivisible spheres; later experiments revealed internal structure (electrons, nucleus).
14. Which subatomic particle has a very small mass and a negative charge?
Electrons are negatively charged and their mass is much smaller than that of protons and neutrons.
15. Which property mainly determines the chemical identity of an element?
The proton number (atomic number) defines the element (e.g., 6 protons = carbon).
16. A neutral chlorine atom has 17 electrons. What is the number of electrons in a chloride ion (Cl^-)?
A chloride ion has gained one electron, so 17 + 1 = 18 electrons.
17. Which hydrogen isotope has one proton and two neutrons?
Tritium (³H) has one proton and two neutrons. Deuterium has one proton and one neutron; protium has no neutrons.
18. Approximately how many atomic mass units (amu) is the mass of a proton?
A proton has mass close to 1 atomic mass unit; neutrons are about 1 amu, electrons are much smaller (~0.0005 amu).
19. Which subatomic particle carries no electrical charge?
Neutrons are electrically neutral; protons are positive and electrons negative (positrons are positive electrons).
20. What causes bright lines in an element’s emission spectrum?
When excited electrons fall to lower levels they emit photons of specific energies, producing line spectra used in analysis.
21. What is the electronic configuration of sodium (Na, atomic number 11) in terms of electrons per shell?
Sodium has 11 electrons: 2 in the first shell, 8 in the second, and 1 in the third (valence electron).
22. How many electrons does a Mg2+ ion have? (Magnesium atomic number 12)
Neutral Mg has 12 electrons; Mg2+ has lost two electrons so 12 − 2 = 10 electrons.
23. Relative atomic mass shown on the periodic table is best described as:
Relative atomic mass reflects the average of isotope masses according to their natural abundance, not just one isotope.
24. Potassium (K) has atomic number 19 and mass number 39. How many neutrons does it have?
Neutrons = mass number − atomic number = 39 − 19 = 20.