Physical and Chemical Properties of Metals, Metalloids and Non-metals

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Physical and chemical properties
	Metals	Metalloids	Nonmetals
Form and structure
Colour	nearly all are shiny and grey-white Cu, Cs, Au: shiny and golden	shiny and grey-white	most are colourless or dull red, yellow, green, or intermediate shades C, P, Se, I: shiny and grey-white
Reflectivity	intermediate to typically high	intermediate	zero or low (mostly) to intermediate
Form	almost all solid Rb, Cs, Fr, Ga, Hg: liquid at/near stp	all solid	most are gases C, P, S, Se, I: solid; Br: liquid
Density	generally high, with some exceptions such as the alkali metals	lower than nearby metals but higher than nearby nonmetals	often low
Deformability (as a solid)	most are ductile and malleable some are brittle (Cr, Mn, Ga, Ru, W, Os, Bi)	brittle	brittle, when solid some (C, P, S, Se) have non-brittle forms
Poisson's ratio	low to high	low to intermediate	low to intermediate
Crystalline structure at freezing point	most are hexagonal or cubic Ga, U, Np: orthorhombic; In, Sn, Pa: tetragonal; Sm, Hg, Bi: rhombohedral; Pu: monoclinic	B, As, Sb: rhombohedral Si, Ge: cubic Te: hexagonal	H, He, C, N, Se: hexagonal O, F, Ne, P, Ar, Kr, Xe, Rn: cubic S, Cl, Br, I: orthorhombic
Packing & coordination number	close-packed crystal structures high coordination numbers	relatively open crystal structures medium coordination numbers	open structures low coordination numbers
Atomic radius (calculated)	intermediate to very large 112–298 pm, average 187	small to intermediate: B, Si, Ge, As, Sb, Te 87–123 pm, average 115.5 pm	very small to intermediate 31–120 pm, average 76.4 pm
Allotropes	around half form allotropes one (Sn) has a metalloid-like allotrope (grey Sn, which forms below 13.2 °C)	all or nearly all form allotropes some (e.g. red B, yellow As) are more nonmetallic in nature	some form allotropes some (e.g. graphitic C, black P, grey Se) are more metalloidal or metallic in nature
Electron-related
Periodic table block	s, p, d, f	p	s, p
Outer s and p electrons	few in number (1–3) except 0 (Pd); 4 (Sn, Pb, Fl); 5 (Bi); 6 (Po)	medium number (3–7)	high number (4–8) except 1 (H); 2 (He)
Electron bands: (valence, conduction)	nearly all have substantial band overlap Bi: has slight band overlap (semimetal)	most have narrow band gap (semiconductors) As, Sb are semimetals	most have wide band gap (insulators) C (graphite): a semimetal P (black), Se, I: semiconductors
Electron behaviour	"free" electrons (facilitating electrical and thermal conductivity)	valence electrons less freely delocalized; considerable covalent bonding present have Goldhammer-Herzfeld criterion ratios straddling unity	no, few, or directionally confined "free" electrons (generally hampering electrical and thermal conductivity)
Electrical conductivity	good to high	intermediate to good	poor to good
... as a liquid	falls gradually as temperature rises	most behave like metals	increases as temperature rises
Thermodynamics
Thermal conductivity	medium to high	mostly intermediate; Si is high	almost negligible to very high
Temperature coefficient of resistance	nearly all positive (Pu is negative)	negative (B, Si, Ge, Te) or positive (As, Sb)	nearly all negative (C, as graphite, is positive in the direction of its planes)
Melting point	mostly high	mostly high	mostly low
Melting behaviour	volume generally expands	some contract, unlike (most) metals	volume generally expands
Enthalpy of fusion	low to high	intermediate to very high	very low to low (except C: very high)
Elemental chemistry
Overall behaviour	metallic	nonmetallic	nonmetallic
Ion formation	tend to form cations	some tendency to form anions in water solution chemistry dominated by formation and reactions of oxyanions	tend to form anions
Bonds	seldom form covalent compounds	form salts as well as covalent compounds	form many covalent compounds
Oxidation number	nearly always positive	positive or negative	positive or negative
Ionization energy	relatively low	intermediate	high
Electronegativity	usually low	close to 2, i.e., 1.9–2.2	high
Combined form chemistry
With metals	form alloys	can form alloys	form ionic or interstitial compounds
With carbon	carbides and organometallic compounds	same as metals	carbon-nonmetal (e.g. CO2, CS2) or organic (e.g. CH4, C6H12O6) compounds
With hydrogen (hydrides)	ionic, with alkali, alkaline earth metals metallic, with transition metals covalent, with post-transition metals	covalent, volatile hydrides	covalent, gaseous or liquid hydrides
With oxygen (oxides)	nearly all solid (Mn2O7 is a liquid) very few glass formers lower oxides: ionic and basic higher oxides: more covalent, acidic	solid glass formers (B, Si, Ge, As, Sb, Te) polymeric in structure; tend to be amphoteric or weakly acidic	solid, liquid or gaseous few glass formers (P, S, Se) covalent, acidic
With sulfur (sulfates)	do form	most form	some form
With halogens (halides, esp. chlorides) (see also)	typically ionic, involatile generally insoluble in organic solvents mostly water-soluble (not hydrolysed) more covalent, volatile, and susceptible to hydrolysis and organic solvents with higher halogens and weaker metals	covalent, volatile usually dissolve in organic solvents partly or completely hydrolysed some reversibly hydrolysed	covalent, volatile usually dissolve in organic solvents generally completely or extensively hydrolyzed not always susceptible to hydrolysis if parent nonmetal at maximum covalency for period e.g. CF4, SF6 (then nil reaction)
Environmental chemistry
Molar composition of Earth's ecosphere	about 14%, mostly Al, Na, Ng, Ca, Fe, K	about 17%, mostly Si	about 69%, mostly O, H
Primary form on Earth	most occur in combined states, as carbonates, silicates, phosphates, oxides, sulfides, or halides some (e.g. Au, Cu, Ag, Pt) occur in free or uncombined states	all occur in combined states, as borates, silicates, sulfides, or tellurides	elemental C, N, O, S, noble gases are plentiful H, F, Se occur primarily in compounds P, Cl, Br, I occur only in compounds, as phosphates, oxides, selenides or halides
Required by mammals	large amounts needed: Na, Mg, K, Ca trace amounts needed of some others	trace amounts needed: B, Si, As	large amounts needed: H, C, N, O, P, S, Cl trace amounts needed: Se, Br, I, possibly F only noble gases not needed
Composition of the human body, by weight	about 1.5% Ca traces of most others through 92U	trace amounts of B, Si, Ge, As, Sb, Te	about 97% O, C, H, N, P others detectable except noble gases

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