ElementsElements

p.p.

The first periodic table was published in 1869 The first periodic table was published in 1869 by Mendeleev.by Mendeleev.

The periodic table is arranged by atomic The periodic table is arranged by atomic number today and no longer by atomic mass.number today and no longer by atomic mass.

The properties of an element can be The properties of an element can be predicted from its location in the periodic predicted from its location in the periodic table.table.

Each square contains the element’s Each square contains the element’s atomic #, chemical symbol, name, and atomic #, chemical symbol, name, and atomic mass.atomic mass.

Fe

26

Iron

55.847

Atomic #

Chemical symbolElement NameAtomic Mass

Periodic Table—is a chemist’s calendarPeriodic Table—is a chemist’s calendar

Atomic Mass—the average mass of all the Atomic Mass—the average mass of all the isotopes of an elementisotopes of an element

There is a pattern of properties when the There is a pattern of properties when the elements are arranged in order of elements are arranged in order of increasing atomic mass.increasing atomic mass.

Atomic # increases from left to right.Atomic # increases from left to right.

Periods—horizontal rows that the table is Periods—horizontal rows that the table is organized into: each period contains a organized into: each period contains a series of different elements.series of different elements.

Groups—(also known as families) 18 Groups—(also known as families) 18 vertical columns—elements in the same vertical columns—elements in the same group/family have similar properties.group/family have similar properties.

Elements on the left side of the periodic Elements on the left side of the periodic table are the most reactive.table are the most reactive.

Elements on the right side of the periodic Elements on the right side of the periodic table are the least reactive.table are the least reactive.

4 Sentence Summary and 4 Study 4 Sentence Summary and 4 Study QuestionsQuestions

Summary StarterSummary Starter

The Periodic Table of elements organizes The Periodic Table of elements organizes the elements like a calendar according to the elements like a calendar according to their masses and other properties.their masses and other properties.

Calculating number of neutronsCalculating number of neutrons

Atomic # = # of protonsAtomic # = # of protonsAtomic # also = # of electronsAtomic # also = # of electrons

H atomic # 1 has ___ protons and ___ electronsH atomic # 1 has ___ protons and ___ electrons

# of neutrons = atomic mass - atomic number# of neutrons = atomic mass - atomic number

H atomic mass ___ - ___ = ___ neutronsH atomic mass ___ - ___ = ___ neutrons