# Studying atoms - images.schoolinsites.com

STUDYING ATOMS Ch. 4.1 True False Statement Daltons atomic theory said all matter is made of atoms, which can be divided Thomsons atomic model, showed that atoms are even smaller than thought Rutherfords atomic model showed that the positive charge is contained in the nucleus Thomsons model is also called the plum pudding model

Rutherford was the 1st to propose an atomic theory True False Greek Atom- 2500 years ago Democritus- Greek philosopher Atom from atomos uncut, indivisible Different types of atoms with different

properties Aristotle's Model : Daltons Atomic Theory1800s Evidence Measured masses of compounds Found that the ratio of masses of the elements in a

compound is always the same Fixed composition! Theory All elements are composed of atoms All atoms of the same element have the same

mass, and atoms of different elements have different masses Compounds contain atoms of more than 1 element In a particular compound, atoms of different elements always combine in the same way Dalton Summed Up: All matter is made of individual particles, called atoms, which cannot be divided! Thomsons Experiment

Glass tube without air 1 side positive, 1 side negative Glowing beam appears in middle Thomsons Model of the Atom-1870s Evidence Negative charge attracted to positive charge 1st evidence atoms are made

of even smaller particles Model Atom = neutral Negative and positive evenly mixed Called Plum Pudding after English dessert

Rutherfords Experiment Aimed alpha particles at gold screen Screen flash when struck by alpha particle Traced path of alpha particles Rutherfords Atomic Theory-1900s Evidence

Alpha particles- fast moving positive charge Positive is not evenly spread Nucleus- dense, positively charged mass at atoms center Theory All of an atoms positive charge is

concentrated in the nucleus THE STRUCTURE OF AN ATOM Ch. 4.2 True False Statement Isotopes have the same atomic #, but different masses due to protons The atomic # equals the # of protons in the element The mass # is the sum of the protons and electrons

Protons and neutrons have almost identical masses Protons, neutrons and electrons are subatomic particles of the atom True False Subatomic Particles Protons- Rutherford Electrons- Thomson

Positively charged particle found in the nucleus Same as atomic # Negatively charged particle found outside the nucleus Atomic # - charge Neutrons- Chadwick Neutral particle found in nucleus Mass almost exact to the proton Mass # - Atomic #

Comparing Subatomic Particles Particle Symbol Charge Relative Mass Actual Mass Electron e- 1-

1/1836 9.11 x 10-28 Proton p+ 1+ 1 1.674 x 10-24 Neutron n

0 1 1.674 x 10-24 Proton and neutrons= same ________ Atomic Number Atoms of any given element always have the same # of p+ Every p+ is balanced by e- for a

neutral charge = # of e- in an atom of that element = the # of p+ in an atom of that element Because atoms are neutral! Mass Number

= p+ + n Ex: Al 13 p+ 14 n Mass # = 27 n = mass # atomic #

Ex: Al Mass # = 27 Atomic # = 13 n= 27-13 14 Practice Symbol Na K P O W

Atomic # Mass # 23 Protons Electron Neutron s s 12 Isotopes

Every element does have the same # of protons and electrons Neutrons can vary Have the same atomic #, but different mass # due to neutrons Practice Symbol

Atomic # Mass # Protons Electron Neutron s s Be Be+2 Cl Cl-1 Na+3 4

9 4 2 5 MODERN ATOMIC THEORY Ch. 4.3 True False Statement Bohrs model focused on electrons, and was adapted from Thomson

Electrons can jump energy levels by gaining or losing energy Electron clouds are the likely areas in which you can find electrons The higher the energy the fewer the atomic orbitals; the lower the energy the higher # of orbitals Electron configuration is based on lettering the periodic table- s, p d, and e True False Bohrs Model

Partnered with Rutherford Focused on electrons Count the # of electrons, and place in orbit Energy Levels Energies that electrons can

have Electrons move levels when the atom gains or loses energy Use with Bohr Models Practice B Si

Mg Ne Electron Cloud Model Improved Bohr Model

Visual model for most likely locations for electrons Dense= electrons Atomic Orbital's Electron cloud = good approximation of how electrons behave in orbitals Energy Level # of Orbitals Max # of Electrons 1

1 2 2 2 8 3 9 18 4

16 32 Electron Configuration Arrangement of electrons in the orbitals Most stable = electrons in orbitals with lowest energy Ground State= all electrons have lowest energies C= 1s22s22p2 Cr= 1s22s22p63s23p64s23d4

Practice Li Mg K Lewis Dot Structures Count valance electrons (outer

layer of electrons) Place around element, no more than 8 Examples and rules for compounds Practice P

CO2 Be HCl Ca NaCl

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