chm bond and reaction Flashcards
How are salt and sugar composed?
- table salt (Nacl) -> composde of ions: electrolyte
- granulated sugar (C12H22O11) -> composde of molecules: nonelectrolyte
In which 3 groups can chemica forces be classified?
- ionic bonds
- covalent bonds
- metallic bonds
What are ionic bonds?
electrostatic forces that exist btw ions of opposite charge; ions may formed from atoms by transfer of electrons (generally result from interaction of metals with nonmetals)
What are covalent bonds?
- result from sharing of electrons btw two atoms (generally seen in interactions of nonmetallic elements with one another)
- H + H -> H2
What are metallic bonds?
- found in solid metals such as copper, iron, and aluminium; in metals each metal atom is bonded to several neighboring atoms ; bonding electrons are free to move throught the 3d structure
- > metallic bonds give rise to typical metallic propertues such as high electrical conductivity and luster (Glanz)
What are valence electrons?
- electrons that are involved in chemical bonding
- they reside (wohnen) in the incompletly filled outer electron shell of an atom
- are shown as Electron-dot smbols (lewis Symbol
How do you know the amout of valence electrons?
-is the same as the group number of the element in the periodic table
What do you know about noble gases?
- atom gain, lose or share electrons to achieve the same number of electrons as the noble gas closest to them in the periodic table
- noble gases are very stable: general lack of chemical reactivity
- all noble gases (execpt He) have eight valence electrons: octet rule
Give an example for an ionic bonding
- NaCl
- when a sodium metal is brought into contact with chlorine gas, a violent reaction ensues (erfolgt)
- product of this very exothermic reaction is NaCl (s)
- > Na + Cl-> Na + + Cl-
- each Na+ ion is surrounded by 6 Cl- ions/ each Cl- is surrounded by 6 Na+
When does an Ionic bond occur?
- when the atoms involved differ greatly in their attraction for electrons
- Na (metal): low ionization energy
- Cl (nonmetal): high affinity for electrons
What is the lattice energy?
-energy required to completly seperate a mole of a solid ionic compund into its gaseous ions
What do you know about the sizes of ions?
- the size of an ion depends on:
- its nuclear chare
- the number of electrons it possesses
- the orbitals in which the outer-shell relectrons reside
- cations (+) are smaller than their parent atoms
- anions are larger than their parent atoms
- ions of the same charge, size increases as we go down a group in periodic table
- for isoelectronic ions, the size of the ion decreases with increasing nuclear charge
What is nonpolar covalent bond and polar covalent bond?
- Nonpolar covalent bond: electrons are shared equally btw two atoms
- Polar covalent bond: one of the atoms exerts (geltend machen) a greater attraction for the bonding electrons than the other.
Give the definition of Electronegativity, Ionization energy and Electron affinity
- Electronegativity: ability of an atom in a molecule to attract electrons to itself
- Ionization energy: measures how strongly the atom holds on to its electrons; the energy necessary to remove an electron from the neutral atom
- Electron affinity: measure of how strongly the atom attracts additional electrons
How does the electroneativity change in the periodic table?
- from left to right increases
- from top to bottom decreases
