Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Atom An atom consists of a • nucleus –(of protons and neutrons) • electrons in space about the nucleus. Electron cloud Nucleus • An atom is the smallest particle of an element that has the chemical properties of the element. • The atom is extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water. • If a large sports stadium were an atom, a marble would represent the nucleus. ATOMIC COMPOSITION • Protons (p+) – + electrical charge – mass = 1.672623 x 10-24 g – relative mass = 1.007 atomic mass units (amu) but we can round to 1 for mass. • Electrons (e-) – negative electrical charge – relative mass = 0.0005 amu but we can round to 0 for mass. • Neutrons (no) no electrical charge – mass = 1.009 amu but we can round to 1 for mass. – Atomic Number, Z All atoms of the same element have the same number of protons in the nucleus, Z 13 Al 26.981 Atomic number Atom symbol AVERAGE Atomic Mass Mass Number, A • C-12, atom with 6 protons and 6 neutrons is the mass standard • = 12 atomic mass units (amu) • Mass Number (A) = # protons + # neutrons • NOT on the periodic table Isotopes • Atoms of the same element (same Z) but different mass number (A). • Boron-10 (10B) has 5 p and 5 n • Boron-11 (11B) has 5 p and 6 n 11B 10B Figure 3.10: Two isotopes of sodium. Atomic Symbols Hyphen notation/mass notation - show the name of the element, a hyphen, and the mass number in sodium-23 Nuclear symbol - show the mass number and atomic number in mass number 23 Na atomic number 11 Isotopes? Which of the following represent isotopes of the same element? Which element? 234 92 X 234 93 X 235 92 X 238 92 X 1. An __ ___ is the smallest particle of an element that has the chemical properties of the element. 2. The 3 pieces of the atom are ________, _________, and _________. 3. Atoms with the same number of protons and electrons, but a different number of neutrons are called ____________. 4. ___________ was an English scientist who developed an atomic theory in the early 1800s.