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G. Chemistry 2

Building blocks: structure of matter

Research: Watch at least one video (should be short videos) on each of the following

  1. relate elements and the periodic table
  2. chemical bonds: ionic, covalent, metallic

Further studies

electron configuration: why are electrons on different shells? why two move on one orbital? 


Dalton’s Atomic theory

Atom is defined as the smallest particle in a chemical reaction. (assumptions of the Dalton’s chemistry which is questionable.) 

  • An element is composed of tiny particles called atoms. all atoms show the same chemical properties. 
  • the law of conservation of mass (stationary of atoms): In an ordinary chemical reaction, atoms move from one substance to another, but no atom of any element disappears or changed into an atom of another element. That is, if atoms are conserved in a reaction, mass will also be conserved. 
  • the law of constant composition: a compound always contains the same elements in the same proportions by mass. If the atom ratio of the elements in a compound is fixed, their promotions by mass must also be fixed. Compounds are formed when atoms of two or more elements combine. In a given compound, the relative numbers of atoms of each kind are definite and constant. (structure or composition does not change: proportion of each element relative to total/other elements stays same. Ratios

The law of multiple proportions: this law is crucial to establishing atomic theory. It applies to situations in which two elements form more than more than one compound. The law states in these compounds, the masses of one element that combine with a fixed mass of the second element (made this one to one unit) are in a ratio of small whole numbers. 

The validity of this law depends on the fact that atoms combine in simple, whole-number ratios. 

Atom is like a tiny universe: the sun = nucleus (protons + neutrons) attracting electron around it; electron = the atmosphere  around the sun

negatively charged particles

every atom contains a definite number of electrons.

Electron configuration: how these electrons are arranged relative to one another. shells

in the outer regions of the atom, where they form what amounts to a cloud of negative charge. 

Rutherford’s alpha particle scattering experiment: before this experiment, it was believed that positive and negative particles were more or less uniformly distributed throughout the atom. 

Nucleus: positive charged, at the center of the atom. 


Atomic number: Z = # of protons

A neutral atom, # of protons = # of electrons (negative = positive)

Mass number: A =  Z + # of neutrons

isotopes: atoms with same Z but different A. 

nuclear symbol 



Whether or not a given nucleus will be stable depends on its neutron:proton ratio. 

Figure 2.5

Radioactivity -> transmutation of elements

research: nuclear radiation


The periodic table

Element: pure (from chapter 1) -> a substance with the same Z. Z determines an element’s chemical properties. 

the table is an arrangement of elements, in order of increasing Z, in horizontal rows of such a length that elements with similar properties fall directly beneath one another in vertical groups. 

how come? since Z determines an element’s property. how come another element beneath it with larger Z share the similar property. 

Notes from the two videos below:

  1. the number of shells decide the rows;
  2. the number of electrons on the out shell and valency decides the columns 


  • building blocks of several elements and many compounds
  • molecular substances are identified by their formulas or names. 
  • two or more atoms may combine to form an uncharged molecule.
  • covalent bonds consist of shared pairs of electrons. (see the video)
  • can be found in nature

molecular formulas

structural formulas

condensed structural formula: suggests the binding pattern in the molecule and highlights the presence of a reactive group of atoms within the molecule. 


  • why pairs of electrons? H2, not H3, or H4? 
  • shell is full or not full: what does this mean? what decides how many electrons it can take? inner shell and out shell? valency. what decides how many shells an atom has?


  • Noble gas: lonely gas
  • valency: the number of bonds that an atom can make. Atoms with same valency is on the vertical column in the table. 



  • species of opposite charge found in all ionic compounds
  • relatively principles to derive the formula and names of ionic compounds

when an atom loses or gains electrons, charged particles called ions are formed. 

  • metals form cations
  • nonmetals form anions
  • C, P, and the metalloids do not form monatomic ions. 

monatomic ions
polyatomic ions (charged molecules)

a bulk sample of matter is electrically neutral, therefore, ionic compounds always contains both cations and anions. 

table salt: There are no discrete molecules; Na+ and Cl- ions are bonded together in a continuous network. 

ionic bonds (vs covalent bonds in molecules)

strong electrolyte

Formulas of ionic compounds

Table 2.2 Some common polyatomic ions


Names of Compounds

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