ElementsElements

p. 33p. 33

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.

SummarySummary

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

Where do Elements come from?Where do Elements come from?

Elements are the simplest substances Elements are the simplest substances from which other forms of matter made.from which other forms of matter made.

The sun is made up of mostly one The sun is made up of mostly one element: Hydrogen. It exists at element: Hydrogen. It exists at tremendously high pressures and at tremendously high pressures and at temperatures as hot as 15 million degrees temperatures as hot as 15 million degrees celsius.celsius.

In conditions such as these, matter cannot In conditions such as these, matter cannot exist as a solid, liquid, or gas, Instead it is exist as a solid, liquid, or gas, Instead it is plasma.plasma.

Plasma—a state of matter that consists of Plasma—a state of matter that consists of a gas-like mixture of free electrons & a gas-like mixture of free electrons & nuclei of atoms that have been stripped of nuclei of atoms that have been stripped of all electrons.all electrons.

Nuclear Fusion: a process in which 2 Nuclear Fusion: a process in which 2 atomic nuclei combine, forming a larger atomic nuclei combine, forming a larger nucleus and releasing huge amounts of nucleus and releasing huge amounts of energy.energy.This process combines smaller nuclei into This process combines smaller nuclei into larger nuclei, creating heavier elements.larger nuclei, creating heavier elements.

These heavier elements include carbon, These heavier elements include carbon, nitrogen and oxygennitrogen and oxygen

SummarySummary

Nuclear fusion combines smaller nuclei Nuclear fusion combines smaller nuclei into larger ones.into larger ones.

To get energy powerful enough to create To get energy powerful enough to create these heavy elements, a Supernova these heavy elements, a Supernova occurs.occurs.

These elements are blown into space.These elements are blown into space.

Supernovas create the heavy elements Supernovas create the heavy elements such as carbon, nitrogen, and oxygen.such as carbon, nitrogen, and oxygen.