Question : Is CoS ( Cobalt (II) Sulfide ) an ionic or covalent bond ?
Answer : CoS ( Cobalt (II) Sulfide ) is an Ionic bond

CoS ( Cobalt (II) Sulfide ) is an Ionic bond
What is chemical bond, ionic bond, covalent bond?
Chemical bond
A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the electrostatic force of attraction between oppositely charged ions as in ionic bonds; or through the sharing of electrons as in covalent bonds .
https://en.wikipedia.org/wiki/Chemical_bond

ionic

Ionic bonding
Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions, and is the primary interaction occurring in ionic compounds.  The ions are atoms that have gained one or more electrons (known as anions, which are negatively charged) and atoms that have lost one or more electrons (known as cations, which are positively charged).
https://en.wikipedia.org/wiki/Ionic_bonding

covalent or molecular

Covalent bond
A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding.
https://en.wikipedia.org/wiki/Covalent_bond

LIST IONIC
(NH4)2CO3
(nh4)2so4
AgCl
agno3
Al2(CO3)3 ( Aluminum Carbonate )
Al2O3
Al2S3
alf3 
aluminum nitrate
aluminum oxide
aluminum sulfate
aluminum sulfide
ammonium
ammonium bromide
ammonium chloride
ammonium hydroxide
ammonium nitrate
ammonium sulfate
Ba(ClO4)2
Ba(OH)2
BaCl2
baking soda
BaO
Barium Chloride
Barium Fluoride
barium oxide
Barium Sulfate
BaS ( Barium Sulfide )
bef2
Ca(NO3)2
Ca3(PO4)2 ( Tricalcium phosphate )
CaBr2 ( Calcium bromide )
CaCl2
CaF2
cah2
CaI2
Calcium chloride
calcium fluoride
calcium nitrate
calcium oxide
Calcium Phosphate
CaO
CaS
CaSO4
Cobalt (II) Nitrate
CoCl2
copper
CsCl ( Cesium Chloride )
CsF ( Cesium Fluoride )
Cu(NO3)2
CuCl2
CuO
CuSO4 
Fe(NO3)3
Fe2O3
FeCl3
FeSO4
hydrogen iodide 
Iron (III) Bromide ( FeBr3 )
iron iii
Iron III Oxide 
iron oxide
k20
K2O
K2S
K2SO4
K3PO4
kbr
KCl
KF
KI
Kl
kmno4
KNO3
KOH
Li2O ( Lithium Oxide )
libr ( Lithium Bromide )
licl
LiF
lih aluminium chloride
LiI ( lithium iodide )
lithium acetate
lithium chloride 
lithium fluoride
Magnesium
magnesium chloride
magnesium iodide
magnesium nitride
magnesium oxide
Magnesium Phosphate ( Mg3(PO4)2 )
magnesium sulfate
mg
Mg(NO3)2
Mg3N2
MgBr2 ( Magnesium Bromide )
mgcl2
MgF2
MgO
MgSO4
MnO2 
na
Na2CO3
Na2O
Na2S
Na3PO4
NaBr
NaCl
NaF
nah
nahco3 ( sodium hydrogen carbonate )
NaI
NaNH2
NaNO3 ( Sodium Nitrate )
NaOCH3
NaOH
NH4
NH4Cl
NH4ClO3
NH4NO2
NH4NO3
NH4OH
no3
NO3-1
phosphoric acid ( H3PO4 )
potassium bromide
potassium carbonate ( K2CO3 )
potassium chloride
potassium iodide
potassium nitrate
potassium oxide
Rb2O
RbCl
salt
silver chloride
silver phosphate
sodium bicarbonate
sodium bromide
sodium carbonate
Sodium Chloride
sodium fluoride
sodium hydroxide
sodium hypochlorite
sodium iodide
sodium oxide
sodium sulfate
sodium sulfide
SrCl2 ( Strontium Chloride )
SrO ( Strontium Oxide )
sulfur hexafluoride

Ca(OH)2 ( Calcium Hydroxide )
MgS ( Magnesium Sulfide )
Ammonium Phosphate ( (NH4)3PO4 )
sodium citrate
CsBr ( Cesium Bromide )
Ammonium Carbonate ( (NH4)2CO3 )
Iron (II) Chloride ( FeCl2 )
Potassium Dichromate ( K2Cr2O7 )
Lithium Hydroxide ( LiOH )
sodium borate 
Strontium Iodide ( SrI2 )
NH4F ( Ammonium Fluoride )
Strontium Fluoride ( SrF2 )
ZnI2 ( Zinc Iodide )
CoS ( Cobalt (II) Sulfide )
NiCl2 ( Nickel (II) Chloride )
HClO4 ( Perchloric acid )
Barium Bromide ( BaBr2 )
sodium aluminum phosphate
Cesium Oxide ( Cs2O )
CuCl ( Copper (I) Chloride )
CsI ( Cesium Iodide )
Potassium Cyanide ( KCN )
potassium chromate ( K2CrO4 )
FeCO3 ( Iron (II) Carbonate )
V2S3 ( Vanadium (III) Sulfide )
Lithium Nitrate ( LiNO3 )
Chromium (III) Fluoride  ( CrF3 )
Barium Nitrate ( Ba(NO3)2 )
Calcium Acetate ( Ca(C2H3O2)2 )
Aluminum Hydroxide ( Al(OH)3 )
Calcium Sulfide ( CaS )
Rubidium Sulfide ( Rb2S )
Beryllium Oxide ( BeO )
Potassium Acetate ( KC2H3O2 )
Barium Bromide ( BaBr2 )
bleach
Zinc Bromide ( ZnBr2 )
Lead (II) Sulfate ( PbSO4 )
Lead (II) Sulfide ( PbS )
Potassium Phosphate ( K3PO4 )
Barium Hydroxide ( Ba(OH)2 )
Lithium Carbonate ( Li2CO3 )

LIST COVALENT BOND / MOLECULAR BOND
acetic acid 
acetone
AlCl3
aluminium chloride
aluminum chloride
ammonia
aspirin
b2h4
BCl3
becl2 ( Beryllium Chloride )
benzoic acid
bf3 ( boron trifluoride )
boron trichloride
Br2
BrCl
BrCl
brf
bromine
c12h22o11
C2H4
C6H12O6
C6H6
carbon dioxide
carbon monoxide
carbon tetrachloride
carbon tetrafluoride
CBr4
CCL4
CF4
CH2O
CH3CH3
ch3li
CH3NH2
CH3OH
CH4
ch4o
CHCl3
chlorine
citric acid
Cl2
clf
clo2
CO
CO2
corn starch
CS2
cyclohexane
dextrose
diamond
dinitrogen monoxide
dinitrogen pentoxide
dinitrogen trioxide
distilled water
ethanol
f2
FCl
FeO
fructose
gacl3
glucose
glycerol
H2 
h20
h2o
h2o2
H2S
H2SO3
H2SO4
HBr
HC2H3O2
hcl
hf ( hydrofluoric acid )
hi ( hydriodic acid )
HNO3
Hydrobromic acid
hydrochloric acid
hydrogen bromide
hydrogen chloride
hydrogen fluoride
hydrogen peroxide
i2
icl
iodine
metalloids
methane
methanol
N2
N2O
N2O2
N2O3
N2O4 HCN
N2O5
naphthalene
NBr3
NCl3
NF3
NH3
nitric acid
nitrogen
nitrogen bromide
nitrogen dioxide
nitrogen tribromide
nitrogen trichloride
nitrogen trifluoride
NO
NO2
O2
OF2 ( Oxygen difluoride )
oxygen
P2O5
P4
P4O10 
paraffin wax
PBr3 ( Phosphorus tribromide )
PCL3
PCl5
PF3
PH3
phosphorus pentachloride
phosphorus pentoxide
phosphorus trichloride
phosphorus trifluoride 
polyatomic ions
s8
salicylic acid
SCl2
SF4
SF6
SiCl4
SiF4
silicon dioxide
silicon tetrachloride 
silicon tetrafluoride
SiO2
SO2
SO3
so4
stearic acid
sucrose
sugar
sulfur dioxide
sulfur trioxide
sulfuric acid
tap water
TiBr4
titanium dioxide ( TiO2 )
toluene
vegetable oil
vinegar
water
xef4

hydrogen sulfide
aluminum carbide ( Al4C3 )
hexane ( C6H14 )
SiH4 ( silane )
xenon trioxide ( XeO3 )
seo2 ( Selenium dioxide )
urea
silicon carbide ( SiC )
ozone ( O3 )
pyridoxine hydrochloride 
C2H6 ( Ethane )
Cl2O ( Dichlorine monoxide )
NI3 ( Nitrogen triiodide )
IF5 ( Iodine pentafluoride )
isopropyl alcohol ( C3H8O )
polyethylene
SCl4 ( Sulfur tetrachloride )
PO4 ( Phosphate ) 
CH3COOH ( acetic acid )
lactic acid ( C3H6O3 )
c2h5oh
CCl
graphite
OCl2
butane

Containing both (ionic and covalent)
AlBr3
BaSO4
Caco3
calcium carbonate
magnesium nitrate
na2so4
sodium acetate

We get answers from
Resources
answers.com
answers.yahoo.com
https://en.wikipedia.org
https://en.wikipedia.org/wiki/Chemical_bond
https://en.wikipedia.org/wiki/Covalent_bond
https://en.wikipedia.org/wiki/Ionic_bonding
pubchem.ncbi.nlm.nih.gov
quizlet.com
socratic.org
www.quia.com
www.quora.com
www.reference.com

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Question : Is CoS ( Cobalt (II) Sulfide ) an ionic or covalent bond ?
Answer : CoS ( Cobalt (II) Sulfide ) is an Ionic bond