Covalent bonding Flashcards
what is a covalent bond?
the attraction of a shaired pair of electrons for the nuclei of the bonded atoms
what are lone-pairs?
outer shell electrons that are not involved in bonding
they are important for determining the chemical reactivity and shapes of molecules
Why do group 3 elements not have 8 electrons in their outer shell when covalently bonded?
only has 3 outer shell electrons = can only form 3 covalent bonds
has to settle for less that 8 electrons in the outer shell
what is a dative bond?
both of the elctrons in the covalent bond are provided by the same atom
what is an permenant ion dipole bond?
when the bonded atoms are different charged = the electrons are not equally shared
what does delta symbol mean on an ion-dipole?
the charge is partial - not fully +/-
What is electronegativity?
the ability of an atom to attract bonding electrons in a covalent bond
How does electronegativity change on the periodic table?
increases going left to right
decreases going down a group
What are the three most electronegative atoms?
flourine
chlorine
oxygen
What is the electron pair theory?
states that the electron pairs in the outer shell repel each other and therefore arrange themselves as far away from each other as possible
What oes the shape of molecules depend on?
the no. of electron pairs (bonding pairs/ electron density)
lone pairs
What is a linear molecule?
two regions of electron density and no lone-pairs
angle = 180
eg: co2
What is a trigonal planar molecule?
three regions of electron density, no lone-pairs
angle=120
eg: BF3
What is a tetrahedral molecule?
4 regions of elecrton density and no lone pairs
angle=109.5
eg: CH4
what is an octrahedral molecule?
6 regions of electron density, no lone-pairs
angle = 90
eg: SF6
What is a pyrimidal molecule?
4 regions of electron density , 1 lone-pair, the electrons repell each other to get as far away as possible
angle = 107
eg: NH3
What is a non-linear molecule?
4 regions of electron density, 2 lone pairs
angle = 104.5
eg: H2O
How do lone pairs affect the shapes of molecules?
repel more so decreases angle by 2.5
Why are some molecules polar?
they are very electronegative and the dipoles do not cancel each other out
