Chemistry - Bohr Models, Periodic Table, and Ionic and Molecular Compounds

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Formula of compounds 

• The element that is on the farthest left goes first (ex: HCl, hydrogen is further to the left, so it goes first) 

• A mix of two elements, element in compound  

• Covalent rule: add number before element name (ex: dichloride) 

• Ionic rule: no number before (ex: chloride) 

Bohr models 

Show the number of protons and electrons in an element 

Cation and anions  

• Cations are positive 

• Anions are negative  

Electrons/protons/neutrons 

• Electrons: the negative electrical charge. The atomic number  

• Protons: the positive electrical charge. The atomic number 

• Neutrons: subatomic particle that make up every atom. the mass rounded to the nearest whole number subtracted from the protons 

Isotopes  

• Atoms with the same number of protons but different number of neutrons 

• Sometimes makes mass bigger 

• Some have different physical properties 

First 18 elements 

Hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon, sodium, magnesium, aluminum, silicon, phosphorus, sodium, chlorine, argon  

Covalent  

Two atoms sharing one or more pair of electrons to hold them together 

Valence  

The outer ring, outer orbit 

Groups and periods 

• Groups are up 

• Periods are sideways

Ionic compounds 

• A metal and a non-metal 

• Have high melting point 

• Net charge must be 0 

• Opposite charges attract 

Molecular compounds 

• A non-metal and a non-metal 

• Both in valence shell 

• Covalent bond 

• Non-metals form molecular compounds by sharing valence shells, outer shell