Unit 4 Flashcards
How to determine valence electrons?
Group (column) #
Chemical bonds (forces)
Forces that hold atoms together by transfer or sharing electrons
Covalent bond
Electrons are shared resulting in molecule. Polar and non polar
Ionic bond
Formed from ions + or - in which electrons are transferred. + ions are cations, - ions are anions.
Exothermic energy
Energy released from system to surroundings when a bond is formed or broken.
Electronegativity
Ability of the nucleus of one element to attract electrons of another element to obtain an octet.
Electronegativity generally ______ from left to right within a period.
Increases. As size of atom decreases, there is more attraction to nucleus.
Electronegativity generally ______ from top to bottom within a group.
Decreases. The size of the atom increases as more energy levels are added.Bottom left to top right increases. Higher / / Increases Lower. /
Metals want to lose electrons so they have ____
Low electronegativity. Small attraction for valence electrons.
Nonmetals want to gain electrons so they have _____
High electronegativity. High attraction for valence electrons
The larger the difference between electronegativities of two nonmetals, the more ___ the bond will be
Polar
Ionic bonds en>1.8 in groups ___
1,2,6,7
Polar bonds between 1.8>en>.4
Everything else
Nonpolar covalent bonds if en<.4
C-H only compounds, diatomic elements
Endothermic energy
Absorbed from surroundings to system when a bond is formed or broken.
The reason elements form bonds
Usually to go to lowest energy state
Molecule
Smallest unit of covalently bonded elements