Identifying bonds · Drawing bonds · Properties · Naming · Designing materials · Molecular geometry · Molecular polarity — 126 cards
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Less than 0.5: nonpolar covalent. 0.5 to 1.7: polar covalent. More than 1.7: ionic.
Metallic, ionic, polar covalent and nonpolar covalent.
Ionic. A metal (Na) with a non-metal (Cl): ΔEN = 3.0 − 0.9 = 2.1, so electrons are transferred and the ions attract.
Metallic. Copper is a metal: its + ions sit in a sea of free-moving electrons.
Nonpolar covalent. Two identical non-metal atoms: ΔEN = 0, so the pair is shared equally.
Polar covalent. Two non-metals with ΔEN between 0.5 and 1.7: shared unequally, pulled toward O.
They are transferred from the metal to the non-metal. The metal loses electrons and becomes a + ion; the non-metal gains them and becomes a − ion. The opposite charges attract.
They move freely among the positive metal ions. This "sea of electrons" explains why metals conduct and can be bent.
Nonpolar covalent. Below 0.5 counts as nonpolar covalent.
Ionic. Above about 1.7 between a metal and a non-metal, the electron is transferred: ionic.
Metallic bonds. Two metals: an alloy, held by metallic bonding.
Cl, because it is more electronegative. The shared pair is pulled toward the more electronegative atom, Cl (3.0 vs 2.1).
Both ionic and covalent. Ionic between Na⁺ and NO₃⁻; covalent between N and O inside the nitrate ion.
Whether the shared electrons are shared unequally or equally. Both share electrons. In a polar bond one atom pulls the pair closer.
The difference in electronegativity between the two bonded atoms. ΔEN = larger EN − smaller EN. Under 0.5 nonpolar, 0.5–1.7 polar covalent, over 1.7 ionic.
1 Count valence electrons (adjust for charge). 2 Skeleton with single bonds. 3 Lone pairs on outer atoms, leftovers on the centre. 4 Make multiple bonds if the centre lacks 8.
Each ion in square brackets with its charge outside. The metal ion has no dots; the non-metal ion has 8.
Valence electrons − lone-pair electrons − number of bonds.
One [Ca]²⁺ and two [Cl]⁻, each Cl with 8 dots. Ca gives away 2 electrons, one to each Cl. Charges: 2+ and 2 × 1− add to zero.
24. C 4 + O 3 × 6 = 22, plus 2 for the 2− charge = 24.
8. N 5 + H 4 × 1 = 9, minus 1 for the + charge = 8.
C. Carbon forms the most bonds (4) and is the least electronegative. H is never central.
It can form only one bond. H needs only 2 electrons, so it makes one bond and is always on the outside.
2. 8 electrons: 2 O–H bonds use 4, the other 4 are 2 lone pairs on O.
A triple bond. 10 electrons: N≡N with one lone pair on each N gives both atoms 8.
4. Each dash is one shared pair = 2 electrons. A double bond is 2 pairs.
Square brackets with the charge outside. The charge belongs to the whole ion, so it goes outside the brackets, top right.
The double bond can go to any of the three O atoms; the real ion is a blend. That is resonance. All three N–O bonds are identical in the real ion.
+1. FC = valence − lone-pair electrons − bonds = 5 − 0 − 4 = +1.
C≡C. Higher bond order = more shared pairs = shorter and stronger.
Move a lone pair from an outer atom to make a double bond. You never add electrons. You turn a lone pair into a shared pair.
High melting point, hard but brittle, conduct only when molten or dissolved, often soluble in water.
Conduct heat and electricity as solids, malleable, ductile, shiny, usually high melting points.
Low melting and boiling points, soft, do not conduct.
Very hard, very high melting points, do not conduct (graphite is the exception). Diamond, quartz.
Metallic. Only metals have electrons that are free to move in the solid.
The ions are free to move once it melts. Ions carry the current. In the solid they are locked in the lattice.
A shifted layer puts like charges next to each other, and they repel. A knock moves one layer by one ion: + meets + and − meets −, so the crystal splits.
The ion layers slide while the electron sea keeps holding them. Malleable and ductile: nothing has to break when the layers move.
The forces between its molecules are weak. Melting separates molecules from each other. It does not break the bonds inside them.
Ionic. High melting point, brittle, conducts only when the ions can move: ionic.
Metallic. Lustre, malleability and conduction as a solid all come from the electron sea.
Molecular covalent. Small molecules with weak forces between them: low melting and boiling points.
Covalent network. Every atom is joined to its neighbours by covalent bonds, as in diamond.
The bond gets shorter and stronger. More shared pairs pull the two nuclei closer and take more energy to break.
Water molecules are polar, so they attract each other strongly. Polar molecules attract each other; nonpolar ones have only weak attractions.
A repeating lattice of + and − ions. There is no "NaCl molecule": each Na⁺ is surrounded by Cl⁻ and each Cl⁻ by Na⁺.
mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca.
NH₄⁺, OH⁻, NO₃⁻, NO₂⁻.
CO₃²⁻, HCO₃⁻, SO₄²⁻, SO₃²⁻, PO₄³⁻.
-ide: a single-element ion (chloride, oxide). -ate and -ite: polyatomic ions with oxygen; -ate has one more O than -ite.
Metal first? Ionic: no prefixes; Roman numeral if the metal has several charges; polyatomic ions keep their names. Two non-metals? Covalent: prefixes and -ide.
Groups 1 and 2, aluminium, zinc (2+) and silver (1+).
Dinitrogen pentoxide. Two non-metals: prefixes. The "a" of penta- is dropped before "oxide".
Carbon monoxide. No mono- on the first element, but the second always takes a prefix.
Magnesium chloride. Metal + non-metal: no prefixes. Mg only forms 2+, so no Roman numeral either.
Iron(III) chloride. Three Cl⁻ make 3−, so the iron is Fe³⁺. Iron has more than one charge, so the numeral is needed.
Copper(II) oxide. O is 2−, so the single copper ion must be Cu²⁺.
Copper(I) oxide. O is 2−, shared by two copper ions, so each is Cu⁺.
Sodium nitrate. NO₃⁻ is the polyatomic ion nitrate. Use its own name.
Calcium carbonate. CO₃²⁻ is carbonate. Calcium only forms 2+, so no numeral.
Ammonium sulfate. Two polyatomic ions: ammonium NH₄⁺ and sulfate SO₄²⁻. No prefixes in ionic names.
Phosphorus trichloride. Two non-metals: prefixes, with no mono- on the first element.
Sulfur hexafluoride. Two non-metals: hexa- for 6.
Al₂O₃. Al³⁺ and O²⁻: criss-cross the charge numbers to get Al₂O₃ (6+ and 6−).
Ca(OH)₂. Ca²⁺ needs two OH⁻. Two of the same polyatomic ion go in parentheses.
FeSO₄. Fe²⁺ and SO₄²⁻ balance one to one.
N₂O₄. Read the prefixes as subscripts: di = 2, tetra = 4.
When both elements are non-metals (a covalent compound). Ionic names never use prefixes: the charges fix the ratio.
When the metal can form more than one charge. Iron, copper and most transition metals. Not Na, Ca, Al, Zn or Ag.
Each iron ion has a 3+ charge. The numeral is the charge of the metal ion. The formula is Fe₂O₃.
Sulfite. -ite has one oxygen fewer than -ate: sulfate is SO₄²⁻. Sulfide is S²⁻.
Hydrogen sulfide. When hydrogen comes first it takes no prefix.
Cu(NO₃)₂. Cu²⁺ needs two NO₃⁻, in parentheses.
List the properties the job needs, pick the bond type that gives them, and name the trade-off.
Copper: its free electrons carry current and it can be drawn into wire. Metallic bonding gives conduction in the solid and ductility.
A plastic (molecular covalent): it insulates and bends. Molecular covalent materials have no free charges, so they insulate, and they are flexible.
An ionic ceramic: very high melting point. Strong attraction between the ions means it survives very high temperatures.
Diamond (covalent network): the hardest. In a covalent network every atom is locked in by covalent bonds.
Atoms of a different size stop the layers sliding easily. Sliding layers are what make a pure metal soft. Disrupting them makes it harder and stronger.
Copper and zinc. Brass = Cu + Zn. Bronze = Cu + Sn.
Copper and tin. Bronze = Cu + Sn. Brass = Cu + Zn.
Chromium. Stainless steel is iron + carbon + chromium + nickel.
It is brittle and would shatter. Ionic materials are hard but brittle: fine for a tile, wrong for anything that takes impacts.
They are poor conductors of heat. The metal body conducts heat to the food; the covalent handle keeps the heat from your hand.
A nonpolar covalent material. Water is polar. Nonpolar materials such as wax or nonstick coatings do not attract it.
A homogeneous mixture of a metal with other elements. No new compound forms: the atoms are mixed, still held by metallic bonding.
Ionic. Dissolving frees the ions, and moving ions carry the current.
They conduct heat well. The free electrons carry heat as well as charge.
Covalent network, such as quartz (SiO₂). Network solids are hard with very high melting points, and many are transparent.
List the properties the job needs. Then match those properties to the bond type that gives them.
Linear 180° · trigonal planar 120° · bent <120° · tetrahedral 109.5° · trigonal pyramidal ≈107° · bent ≈104.5°.
Each bonded atom (single, double or triple bond counts once) and each lone pair on the central atom.
Electron geometry counts all domains. Molecular geometry names only where the atoms are.
2. Two double bonds, and each counts as one domain.
Tetrahedral. 4 bonded atoms and no lone pairs on C.
Trigonal pyramidal. 4 domains: 3 atoms + 1 lone pair.
Bent. 4 domains: 2 atoms + 2 lone pairs.
Linear. 2 domains and no lone pairs on C.
Trigonal planar. 3 domains and no lone pair on B.
Bent. 3 domains: 2 atoms + 1 lone pair on S.
109.5°. Four domains point to the corners of a tetrahedron.
About 104.5°. Two lone pairs squeeze the angle below 109.5°.
120°. Three domains spread evenly in a plane.
Tetrahedral. Electron geometry counts all 4 domains, lone pair included.
Tetrahedral. 2 bonded atoms + 2 lone pairs = 4 domains.
Bent, a little less than 120°. Only 2 atoms are attached, so the atoms form a bent shape.
The lone pair repels more than a bonding pair. Lone pairs take more space and push the bonds closer together.
The bond comes out of the page, toward you. Plain = in the page, wedge = toward you, dash = away.
Trigonal planar. N has 3 bonded O atoms and no lone pair: 3 domains.
Trigonal pyramidal. 26 electrons: P has 3 bonds + 1 lone pair = 4 domains.
1 Any polar bonds? If not, nonpolar. 2 Lone pair on the central atom? Polar. 3 All outer atoms identical? Nonpolar; if not, polar.
It is linear, so the two equal dipoles cancel. Two equal arrows pointing in opposite directions add to zero.
It is bent, so the two O–H dipoles add instead of cancelling. The shape decides: the two arrows point partly the same way.
No: ΔEN is 0.4. A bond with ΔEN below 0.5 counts as nonpolar.
O. O is more electronegative (3.5 vs 2.1), so it pulls the shared pair.
Its bonds are polar but the molecule is nonpolar. C–Cl is polar (ΔEN 0.5). Four equal dipoles in a tetrahedron cancel.
Its bonds are nonpolar and the molecule is nonpolar. C–H has ΔEN 0.4: no polar bonds, so nothing to add up.
Yes: the outer atoms are not all the same. The C–F dipoles are stronger than the C–Cl dipoles, so they cannot cancel.
Yes: the two ends are different. Linear cancels only when both outer atoms are the same, as in CO₂.
The more electronegative atom. That is where the shared electrons are pulled: the δ− end.
Polar. The lone pair makes the shape unsymmetric, so the dipoles do not cancel.
NF₃: it has a lone pair and is trigonal pyramidal. BF₃ is trigonal planar and symmetric, so its three dipoles cancel.
Yes: it is bent. S has a lone pair, so SO₂ is bent and its S–O dipoles add.
NH₃, because it is polar like water. "Like dissolves like": polar dissolves in polar.
Its shape: whether the bond dipoles cancel. Molecular polarity is the vector sum of the bond dipoles.
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