Quiz om det periodiske system

• A. Krypton
• B. Potassium
• C. Calcium
• D. Phosphorus

Svar: B. Potassium

K comes from kalium, an older name for potassium. Krypton is Kr, calcium is Ca and phosphorus is P. Symbols that do not match the English name usually come from an older Latin or German name, so they are worth learning as a set.

• A. Boron
• B. Nitrogen
• C. Carbon
• D. Oxygen

Svar: C. Carbon

The atomic number is the number of protons, and it is what the table is ordered by. Count along period 2: lithium is 3, beryllium 4, boron 5 and carbon 6. Nitrogen is 7 and oxygen is 8.

A symbol starts with a capital letter and any second letter is lowercase, so Co is the element _____, while CO is the compound _____.

Muligheder for felt 1: cobalt, copper, carbon, chlorine

Muligheder for felt 2: carbon monoxide, cobalt oxide, carbon dioxide, copper oxide

Svar: cobalt, carbon monoxide

Co is one element, cobalt. CO is a carbon atom joined to an oxygen atom, which is carbon monoxide. Carbon dioxide is CO2, and copper is Cu. The capital letter is what tells you where one symbol ends and the next begins.

• A. Fluorine
• B. Bromine
• C. Argon
• D. Chlorine

Svar: D. Chlorine

Period 3 is the third row, which runs from sodium to argon, and group 17 is the halogen column. They meet at chlorine. Fluorine is in group 17 but period 2, bromine is group 17 but period 4, and argon is period 3 but group 18.

Vælg alle, der passer.

• A. Fluorine
• B. Chlorine
• C. Neon
• D. Bromine
• E. Sodium

Svar: A. Fluorine, B. Chlorine, D. Bromine

The halogens are group 17: fluorine, chlorine, bromine, iodine and astatine. Neon is a noble gas in group 18, and sodium is an alkali metal in group 1. The halogen names all end in -ine, which is a handy memory hook.

• A. One valence electron each
• B. The same number of protons
• C. The same number of electron shells
• D. The same atomic mass

Svar: A. One valence electron each

They are all in group 1, so each atom has one electron in its outer shell, and that electron is easy to lose. Protons, shells and mass all differ: each step down the group adds a shell.

Mendeleev arranged his 1869 table mostly by increasing atomic _____. The modern table is arranged by increasing atomic _____.

Muligheder for felt 1: number, mass, radius, charge

Muligheder for felt 2: mass, number, volume, density

Svar: mass, number

Mendeleev ordered the elements mostly by atomic mass and left gaps for elements not yet found. Later work showed that the number of protons, the atomic number, is the better order. A few pairs, such as tellurium and iodine, sit in the opposite order if you go by mass.

• A. 1
• B. 2
• C. 8
• D. 18

Svar: B. 2

Period 1 holds only hydrogen and helium, because the first electron shell fits just 2 electrons. Periods 2 and 3 hold 8 elements each, and the later periods are longer.

• A. They conduct electricity well
• B. They are brittle when solid
• C. They are usually gases at room temperature
• D. They tend to gain electrons

Svar: A. They conduct electricity well

Metals are good conductors of heat and electricity, are usually shiny and can be hammered or drawn into wire. Brittle solids, gases and elements that tend to gain electrons describe nonmetals. Most metals are solid at room temperature, with mercury the usual exception.

Vælg alle, der passer.

• A. Gold: Au
• B. Silver: Si
• C. Lead: Pb
• D. Tin: Ti
• E. Mercury: Hg

Svar: A. Gold: Au, C. Lead: Pb, E. Mercury: Hg

Gold is Au (aurum), lead is Pb (plumbum) and mercury is Hg (hydrargyrum). Silver is Ag (argentum), and Si is silicon. Tin is Sn (stannum), and Ti is titanium.

• A. Sodium
• B. Sulfur
• C. Silicon
• D. Neon

Svar: C. Silicon

Silicon sits on the staircase line between metals and nonmetals and behaves partly like each: it is a semiconductor, which is why it is used in chips. Sodium is a metal, sulfur is a nonmetal and neon is a noble gas. Most tables list boron, silicon, germanium, arsenic, antimony and tellurium as metalloids, though sources differ on a few more.

• A. decreases, because the nucleus holds the electrons tighter
• B. stays the same, because every atom in a group has the same valence electrons
• C. decreases and then increases at the bottom of the group
• D. increases, because each row adds an electron shell

Svar: D. increases, because each row adds an electron shell

Each new period adds an electron shell, so atoms get larger even though the nuclear charge grows. This is why a cesium atom is much bigger than a lithium atom. Across a period the trend runs the other way.

Noble gases such as neon and argon rarely react because their outer electron shell is _____. They fill group _____ of the table.

Muligheder for felt 1: full, empty, half full, metallic

Muligheder for felt 2: 1, 2, 17, 18

Svar: full, 18

A full outer shell is very stable, so noble gases have little reason to gain, lose or share electrons. They fill group 18, the far-right column. Group 17 is the halogens, one electron short of a full shell, and group 1 is the alkali metals.

• A. Oxygen
• B. Chlorine
• C. Fluorine
• D. Nitrogen

Svar: C. Fluorine

Electronegativity measures how strongly an atom pulls on shared electrons. It rises toward the upper right of the table, and fluorine, small and one electron short of a full shell, is the highest of all. The noble gases are left out of this trend because they rarely form bonds.

Vælg alle, der passer.

• A. Metallic character increases
• B. Atomic radius decreases
• C. First ionization energy increases
• D. The number of occupied electron shells increases
• E. Elements change from metals to nonmetals

Svar: B. Atomic radius decreases, C. First ionization energy increases, E. Elements change from metals to nonmetals

Across a period, protons are added while the new electrons go into the same shell, so the pull on the outer electrons grows. Atoms shrink, ionization energy rises with a few small dips, and elements go from metals on the left to nonmetals on the right. Metallic character therefore falls, and the number of shells stays the same within a period.