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Chapter 2 part 2
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What is a molecule?
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What is a molecule?
A
molecule
is a distinct substance formed when two or more atoms are covalently bonded.
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Termini in questo insieme (20)
Nascondere definizioni
What is a molecule?
A
molecule
is a distinct substance formed when two or more atoms are covalently bonded.
What defines a compound?
A
compound
is a molecule containing two or more different elements bonded covalently or ionically.
How do chemical bonds form?
Chemical bonds form when atoms share, donate (lose), or accept (gain) electrons.
How many bonds can hydrogen, carbon, nitrogen, and sodium make?
Hydrogen makes 1 bond, carbon 4, nitrogen 3, and sodium typically 1 bond based on unpaired valence electrons.
What is an ionic bond?
An
ionic bond
forms when one atom donates one or more electrons to another, creating charged ions.
What are cations and anions?
Cations
are positively charged ions;
anions
are negatively charged ions formed by loss or gain of electrons.
Identify the cation and anion in NaCl.
In NaCl,
Na+
is the cation and
Cl-
is the anion.
What is a covalent bond?
A
covalent bond
is the sharing of a pair of valence electrons between two atoms.
Describe the covalent bonding in water (H2O).
In H2O, oxygen shares electrons with two hydrogens, completing each atom's valence shell.
Describe the covalent bonding in methane (CH4).
In CH4, carbon shares electrons with four hydrogens, filling carbon's valence shell.
What is electronegativity?
Electronegativity
is an atom's tendency to attract electrons in a bond.
When is a bond polar or nonpolar?
A bond is
polar
if the electronegativity difference is 0.5 or greater; otherwise, it is
nonpolar
.
Is the bond between hydrogen and carbon polar or nonpolar?
The H-C bond is
nonpolar
due to a small electronegativity difference.
Is the bond between hydrogen and oxygen polar or nonpolar?
The H-O bond is
polar
because oxygen is more electronegative than hydrogen.
What is a hydrogen bond?
A
hydrogen bond
is a noncovalent attraction between a hydrogen atom and an electronegative atom.
What causes polarity in a water molecule?
Unequal sharing of electrons causes oxygen to be slightly negative and hydrogens slightly positive, making water polar.
What are reactants and products in a chemical reaction?
Reactants
are starting substances;
products
are substances formed when chemical bonds are made or broken.
Example of a chemical reaction involving hydrogen and oxygen?
2 H2 + O2 → 2 H2O, where hydrogen and oxygen react to form water.
What is the significance of valence electrons in bonding?
The number of unpaired valence electrons determines how many bonds an atom can form.
What is an emergent property in chemistry?
New properties arise from the arrangement and interaction of parts as complexity increases.