The elements of the periodic table fall into three different groups: metals, metalloids, and nonmetals.
This periodic table shows the three different groups of elements. The metalloid group separates the metals from the nonmetals. Elements to the left are metals and nonmetals are to the right. The exception is the element hydrogen. Hydrogen has properties of a nonmetal at normal temperatures and pressures and characteristics of an alkali metal under extremely high pressure.
Some periodic tables include a zig-zag line that distinguishes between metals and metalloids. The line begins below boron (B) and extends between bismuth (Bi) and polonium (Po) or down between livermorium (Lv) and tennessine (Ts). In reality, the metals near the line often display nonmetallic properties while the nonmetals have some metallic character.
Key Takeaways: Metals, Metalloids, and Nonmetals
- Elements are classified as metals, metalloids, or nonmetals based on their physical and chemical properties.
- Metals are generally shiny, good conductors of heat and electricity, malleable, ductile, and have high melting and boiling points.
- Nonmetals are usually dull, poor conductors of heat and electricity, brittle when solid, and often have lower melting and boiling points.
- Metalloids have properties that are intermediate between metals and nonmetals, making them useful in semiconductor applications.
- Metals tend to lose electrons (forming cations), while nonmetals gain electrons (forming anions); metalloids behave either way depending on the reaction.
- Metals dominate the periodic table, occupying the left and center, while nonmetals are found on the right, and metalloids form a staircase-like boundary between them.
Properties of Metals
Most of the elements are metals. Metals include the alkali metal, alkaline earth, transition metal, basic metal (post-transition metal), lanthanide, and actinide groups. These elements have metallic character, which means atoms easily lose electrons. Metals display the following properties:
- Solid at room temperature (with the exception of mercury)
- Usually shiny, with metallic luster
- High melting point
- Good conductor of heat
- Good conductor of electricity
- Malleable – able to be pounded into sheets
- Ductile – can be pulled into wire
- High density (exceptions: lithium, potassium and sodium)
- Closely packed crystal structures
- Low ionization energies and electronegativities
- Corrode in air or seawater
- Lose electrons in reactions
Examples of elements on the periodic table that are metals include lithium, titanium, silver, lead, and uranium.
Properties of Metalloids or Semimetals
Metalloids or semimetals possess some properties of metals and some of nonmetals. Metalloids typically have several forms or allotropes with very different properties. Characteristics of metalloids include:
- Dull or shiny
- Conduct heat and electricity, but not as well as metals
- Good semiconductors
- Usually malleable
- Usually ductile
- Intermediate ionization energies and electronegativity values
- Can both gain and lose electrons in reactions
Examples of elements that are metalloids include boron, silicon, arsenic, and antimony.
Properties of Nonmetals
The nonmetals include the nonmetals element group, plus the halogens, and noble gases. Properties of nonmetals include:
- Dull, not shiny or metallic
- Poor conductor of heat
- Poor conductor of electricity
- Not malleable or ductile, usually brittle
- Lower density (when compared to metals)
- Lower melting point and boiling points (when compared to metals) – Most are gases at room temperature.
- Relatively high ionization energies and electronegativities
- Gain electrons in reactions
Examples of nonmetals include helium, nitrogen, sulfur, and chlorine.
Test Your Understanding
Check your understanding of metals, metalloids, and nonmetals with this quick 10-question quiz:
- Which category of elements is the best conductor of electricity?
a) Metals
b) Metalloids
c) Nonmetals
d) Noble gases
(Answer: a) Metals) - Which element is a metalloid?
a) Oxygen
b) Silicon
c) Iron
d) Neon
(Answer: b) Silicon) - What is a key characteristic of most nonmetals?
a) They are ductile
b) They conduct electricity well
c) They tend to be brittle in solid form
d) They have high melting points
(Answer: c) They tend to be brittle in solid form) - Which of the following elements is a metal?
a) Sulfur
b) Carbon
c) Copper
d) Arsenic
(Answer: c) Copper) - What type of elements are found along the ‘stair-step’ line on the periodic table?
a) Metals
b) Metalloids
c) Nonmetals
d) Noble gases
(Answer: b) Metalloids) - Which statement is true about metalloids?
a) They are never conductive
b) They can have properties of both metals and nonmetals
c) They are always highly reactive
d) They only exist as gases
(Answer: b) They can have properties of both metals and nonmetals) - Which of the following elements is most likely to gain electrons in a chemical reaction?
a) Sodium (Na)
b) Aluminum (Al)
c) Fluorine (F)
d) Iron (Fe)
(Answer: c) Fluorine (F)) - What is a common use for metalloids like silicon?
a) Electrical wiring
b) Semiconductor devices
c) Making steel alloys
d) Fuel production
(Answer: b) Semiconductor devices) - Which element is liquid at room temperature and classified as a metal?
a) Mercury (Hg)
b) Bromine (Br)
c) Gallium (Ga)
d) Argon (Ar)
(Answer: a) Mercury (Hg)) - Which of the following is NOT a property of most metals?
a) Malleability
b) High conductivity
c) Low density
d) Luster
(Answer: c) Low density (most metals have relatively high density)
References
- Askeland, D.R.; Fulay, P.P.; Wright, J.W. (2011). The Science and Engineering of Materials (6th ed.). Stamford, CT: Cengage Learning. ISBN 0-495-66802-8.
- Brown, T.L.; LeMay, H.E.; et al. (2009). Chemistry: The Central Science (11th ed.). Pearson Education. ISBN 978-0-13-235-848-4.
- Edwards, Peter P.; Sienko, M. J. (1983). “On the occurrence of metallic character in the periodic table of the elements”. Journal of Chemical Education. 60 (9). American Chemical Society (ACS): 691–696. doi:10.1021/ed060p691
- Herzfeld, K. F. (1927). “On Atomic Properties which make an Element a Metal”. Physical Review. 29 (5): 701–705. doi:10.1103/PhysRev.29.701