Periodic table quiz

Answer key

1. Au. Gold uses Au, from the Latin aurum.
2. Hydrogen. Atomic number counts protons. Hydrogen has one proton, so every hydrogen atom has atomic number 1, whatever its isotope or charge.
3. Protons. An element is defined by its proton count. Changing neutrons produces an isotope; changing electrons produces an ion.
4. Sodium. Na is sodium, from the Latin natrium.
5. Helium. Helium is in group 18. Its filled first electron shell makes it very unreactive, which is characteristic of the noble gases.
6. Fe. Iron has the symbol Fe, from the Latin ferrum.
7. Oxygen. O is oxygen. Osmium is Os and oganesson is Og.
8. Carbon. Carbon has six protons. Its isotopes, including carbon-12 and carbon-14, keep those six protons but differ in neutron count.
9. Mercury. Mercury melts at about −39°C, so it is liquid at ordinary room temperature.
10. K. Potassium uses K, from the name kalium.
11. Silver. Ag comes from the Latin name argentum.
12. Copper. Copper’s symbol comes from cuprum.
13. Lead. Pb comes from plumbum, the Latin name for lead.
14. Tin. Sn comes from stannum, the Latin name for tin.
15. Tungsten. The symbol W reflects the alternative name wolfram.
16. Ca. Calcium uses Ca. In a two-letter element symbol the first letter is capitalized and the second is lowercase; C alone is carbon.
17. Magnesium. Mg is magnesium; manganese uses Mn.
18. Aluminum. Aluminum, also spelled aluminium, has atomic number 13.
19. Silicon. Si is silicon; S is sulfur and Ag is silver. Silicon’s semiconducting properties make it useful in electronic devices.
20. Phosphorus. Phosphorus uses P, while potassium uses K.
21. Sulfur. Sulfur is a nonmetal with atomic number 16.
22. Chlorine. Chlorine is a halogen in group 17.
23. Nitrogen. N is nitrogen. Nitrogen gas makes up about 78% of dry air, so it is more abundant in the atmosphere than oxygen.
24. Neon. Neon is a group 18 noble gas. An electrical discharge through neon produces the reddish-orange glow of a true neon sign.
25. Argon. Ar is argon, a noble gas. Its low reactivity makes it useful as a protective atmosphere where other substances must not react with air.
26. Zinc. Zinc coatings help protect steel from corrosion.
27. Nickel. Nickel uses Ni, whereas nitrogen uses N and neon uses Ne. These similar symbols represent different elements.
28. Iodine. Iodine is a halogen; iron uses Fe.
29. Uranium. Uranium is an actinide with atomic number 92.
30. Platinum. Platinum is a metal used in catalysts and jewelry.
31. Helium. Helium has two protons. Its atomic number remains 2 whether the atom is neutral, ionized, or a different isotope.
32. Lithium. Lithium has three protons and is the first metal in group 1. Hydrogen comes above it in the table but is a nonmetal.
33. Oxygen. An oxygen atom has eight protons in its nucleus.
34. Neon. Neon has ten protons and occupies the end of period 2. Its position in group 18 places it among the noble gases.
35. Calcium. Calcium has twenty protons and belongs to group 2. Atomic number is a proton count, not the atom’s total mass.
36. Groups. Groups are the vertical columns. Elements in a group often behave similarly because their outer electrons have related arrangements.
37. Periods. Periods run horizontally. Atomic number increases from left to right across each row of the modern periodic table.
38. Halogens. Fluorine, chlorine, bromine, and iodine belong to the halogens.
39. Noble gases. Group 18 contains helium, neon, argon, and the other noble gases. Their filled outer electron shells help explain their generally low reactivity.
40. Alkaline earth metals. Magnesium and calcium are alkaline earth metals.
41. Alkali metals. Lithium, sodium, and potassium are group 1 alkali metals. Hydrogen sits above them in the table but is not an alkali metal.
42. An electron. Electrons are negatively charged; protons are positively charged.
43. A neutron. A neutron has no net electric charge. Together with positively charged protons, neutrons make up atomic nuclei other than ordinary hydrogen’s.
44. An ion. Losing electrons makes a positive ion; gaining them makes a negative ion. The proton count, and therefore the element’s identity, stays the same.
45. Neutrons. Isotopes have the same number of protons but different numbers of neutrons. Carbon-12 and carbon-14 are therefore both carbon.
46. Protons and neutrons. Mass number is the integer total of protons and neutrons in one nucleus. It differs from the abundance-weighted atomic mass shown on many tables.
47. Carbon. Diamond and graphite are carbon allotropes: the same element with different atomic structures. Those structures give them very different properties.
48. Carbon. Pencil cores use graphite, a form of carbon, mixed with clay.
49. Bromine. Bromine is liquid at 20°C because this temperature is above its melting point and below its boiling point. Mercury is liquid too, but is a metal.
50. Dmitri Mendeleev. Mendeleev published his table in 1869, leaving gaps and predicting properties of missing elements. The modern table is ordered by atomic number.