UNIT: Matter TOPIC: Atoms, Isotopes and Ions Objectives: Lesson 4 of 4 • You will review the structure of the atom • You will learn the difference between the Atomic Number and Mass Number for an element • You will learn what an isotope is • You will learn what an ion is and how they form • You will learn the difference between a cation and anion
Quickwrite In 1-2 sentences answer one of the questions below: • Review: What components do you think make up an atom??? • What is in the nucleus of an atom? • How big is the nucleus of an atom when compared to the entire atom?
Atoms Protons Neutrons • All matter is made of tiny particles called Atoms • An atom is the smallest particle of an element that has the properties of that element • Atoms are composed of a dense center region called a nucleus • The nucleus is made up of positive particles called protons and neutral particles called neutrons • Atoms are also made up of an outer electron “cloud” where negatively charged particles known as electrons can be found - Nucleus + + + + - - + + - Electrons
Actual Size of the Nucleus • Imagine an atom is the size of a baseball stadium • On this scale, the nucleus would be about the size of a pea on the pitcher’s mound • The electron “cloud” and electrons that surround the nucleus would occupy the size of the stadium • The electron cloud is essentially an unoccupied region of space, so an atom is really just empty space + + + + + +
What is an Atom? Protons Neutrons • Smallest particle of an element that has the properties of that element • It is made up of: • An incredibly small, dense center called a nucleus • The nucleus is made up of positively charged particles called protons and neutral particles called neutrons • A region of empty space known as the electron “cloud” where negatively charged particles called electrons can be found - Nucleus + + + + + + - - - Electrons
Atomic Mass Unit (AMU) • A carbon-12 atom has 6 protons & 6 neutrons, so 1 AMU is basically the mass of 1 proton or neutron • Electrons are so light that you can usually ignore their mass relative to the atom as a whole • Remember, all the mass or weight in an atom is in the nucleus • A proton has about 2000 times the mass of an electron • What if we could weigh or mass a proton on a scale? • How much do you think it would it weigh? • The actual mass of a protonis1.66 x 10-24 grams • It turns out that a neutronhas about the same mass: 1.66 x 10-24 grams • That’s an incredibly small number to work with • A more convenient unit to measure the mass of a proton or neutron is the Atomic Mass Unit orAMU • 1 AMU = 1.66 x 10-24 grams and is defined as1/12 the mass of a carbon-12 atom + 1.6 x 10-24gms 1.6 x 10-24gms
What is an Atomic Mass Unit (AMU)? • 1 AMU = 1.66 x 10-24 grams and is defined as1/12 the mass of carbon-12 atom • 1 AMU is the mass or weight of a proton or neutron
Atomic Number and Mass Number • Atomic number is the number of protons each element has • For example, Carbon here has six protons • The numbers of protons determines the identity of the element • The periodic table is listed in order of increasing atomic number • For example, Hydrogen, the lightest element has 1 proton • Helium, the next heaviest element has 2 protons • Lithium has 3 protons……
Atomic Symbol, Atomic Number and Mass Number Atomic Symbol Mass Number • Recall that every element on the periodic table is represented by an atomic symbol • The atomic symbol is a one or two letter symbol used to represent every element on the periodic table • The atomic symbol for Carbon is represented by a capital C • Every Element can also be represented by a mass number and atomic number • The atomic number is the number of protons in the element • Remember, it is the amount of protons that determine the element • Carbon always has 6 protons, so the atomic number is 6 or 6 AMU • Themass number is equal to the number of protons plus neutrons • For carbon, it is 6 protons plus 6 neutrons, which is equal to 12 or 12 AMU C 12 6 Atomic Number
Atomic Symbol, Atomic Number and Mass Number Atomic Symbol Mass Number • Here is a Helium Atom • The atomic symbol for Helium is represented by He • Notice, the nucleus contains two protons, therefore it’s atomic number is 2 or 2 AMU • You may have also noticed that Helium nucleus has 2 two neutrons • Remember, the mass number is equal to the number of protons plus neutrons therefore it’s mass number is equal to 4 or 4 AMU He 4 - + 2 + - Atomic Number Helium-4 2 2 2 4
What is the difference between the Atomic Symbol, Atomic Number and Mass Number? • The atomic symbol is a one or two letter symbol used to represent every element on the periodic table • The mass number is equal to the number of protons plus neutrons • The atomic number is the number of protons in the element • Please draw:
Isotopes • Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons • What would happen if we added another neutron to the nucleus? • How does the mass number change if added another neutron? • Let’s find out and add another neutron • Notice, the number of protons and the atomic number did not change, • Once again, because we added a neutron the mass number increased from 5 to 6 • What would happen if we added another neutron to the nucleus? • How does the mass number change if added another neutron? • Let’s find out and add another neutron • Notice, the number of protons and the atomic number did not change, • However, because we added a neutron the mass number increased from 4 to 5 Atomic Symbol Mass Number He 5 6 4 • Remember, the number of protons determines the atom or element • Lets take a look at our helium atom again • Recall that helium has two neutrons and two protons in its nucleus giving it an atomic number of 2 and a mass number of 4 - - 2 + + Atomic Number 2 Helium-4 2 4 2 2 Helium-5 2 5 3 Helium-6 4 2 6 2
Isotopes • Here we have a Carbon-12 atom with six protons and six neutrons • Carbon-12 is not an isotope because we have an equal amount of protons and neutrons • One of the most common isotopes scientists work with is the Carbon-14 isotope • To make a Carbon-14 isotope, we need to add two neutrons to Carbon-12 seen here • So, let’s add two neutrons to Carbon-12 • Notice, the number of protons and atomic number did not change, but, because we gained two neutrons, the mass number went from 12 to 14 - Atomic Symbol Mass Number C 12 14 - - - 6 + + + + + + Atomic Number - - Carbon-12 NO 6 6 6 12 Carbon-14 6 6 8 14 YES
What is an Isotope? • Atoms of the same element that have the same number of protons but different numbers of neutrons • Example: Carbon-14 ( ) and Helium-6 ( )
Atomic Symbol Mass Number Ions Na 12 14 11 protons (+11 Charge) Sodium Atom 11 electrons (-11 Charge) • A ion is an atom(s) that has lost or gained one or more electrons giving it an overall charge • For example, here we have a neutral Sodium atom • A neutral sodium atom has 11protonsand 11electrons going around the nucleus • What makes it neutral? • Remember, protons have a +1 charge and electrons have -1 charge • The fact that it has an equal amount of protons and electrons gives it a charge of zero • Or we can do the math and see that -11 + 11 = 0 • But sodium is an atom that is known for losing an electron 6 Neutral (+0 charge) - Atomic Number + + + + + + + + + + + - - - - - - - - - -
Atomic Symbol Mass Number Ions Na 12 14 Sodium Atom 11 protons (+11 Charge) • If an ion is an atom(s) that has lost or gained one or more electrons giving it an overall charge, What do you think would happen if sodium here lost an electron? • What kind of charge will the sodium have on it after it loses an electron? • Let’s find out and remove the outer electron • Notice, there are still 11 protonsin the nucleus, but now there are 10 electrons • Because it has an additional proton, the sodium atom now has a +1 charge, forming a +1 Ion • Once we could do the math to verify this: -10 + 11 = +1 6 10 electrons (-10 Charge) +1 - Atomic Number + + + + + + + + + + + - - - - - - - - - -
What is an Ion? • An atom(s) that has lost or gained one or more electrons giving it an overall charge • Example: sodium ion (Na+1)
Cations versus Anions 12 electrons (-12 Charge) 10 electrons (-10 Charge) 12 protons (+12 Charge) Magnesium Atom • A cation is a positive ion because it has lost one or more electrons • For example, here we have a neutral Magnesium atom • A neutral Magnesium atom has 12protonsand 12electrons going around the nucleus • What kind of Ion will form if Magnesium here lost 2electrons? • Let’s find out and remove the outer 2electrons • Because it has two additional protons, the Magnesium atom now has a +2 charge, forming a +2 Cation • Once again we could do the math to verify this: -10 + 12 = +2 • Metals (such as Magnesium) typically lose electrons to become cations +2 - + + + + + + + + + + + - - - - - - - - - -
Cations versus Anions - 9 protons (+9 Charge) Fluorine Atom 9 electrons (+9 Charge) 10 electrons (-10 Charge) • A anion is a negative ion because it has gained one or more electrons • For example, here we have a neutral Fluorine atom • A neutral Fluorineatom has 9protonsand 9electrons going around the nucleus • What kind of Ion will form if Fluorinehere gained 1electron? • Let’s find out and ADD 1electron • Because it has one additional electron, the Fluorine atom now has a -1 charge, forming a -1 anion • Once we could do the math to verify this: -10 + 9 = -1 • Nonmetals (such as Fluorine) typically gain electrons to become anions • When an atom becomes an anion, we change the ending and add -ide -1 - + + + + + + + + + + + - - - - - - - -
What is the difference between a Cation and an Anion? • A cation is a positive ion formed when an atom loses one or more electrons • Metals typically lose electrons to become cations • Example: Sodium (Na1+) & Magnesium (Mg2+) cation • A anion is a negative ion formed when an atom gains one or more electrons • Nonmetals typically gain electrons to become anions • Example: Fluoride (F1-) & Sulfide (S2-) anion
Practice: • Complete the table below Carbon-12 6 6 12 NO 6 0 6 Answer: -Because there are 6 protons, the atomic number must be 6 as well. -The mass number is equal to the amount of protons + neutrons, so the mass number must be 12 -Because the amount of the protons is the same as the amount of neutrons, the atom is NOT an isotope -Because the charge is zero, their must be an equal amount of protons and electrons, so in this case, because there are 6 protons, so, their must be 6 electrons -Since we know the mass number and atomic number, we can write the symbol
H 3 Practice: 1 • Complete the table below 1 YES 3 Hydrogen-3 +1 0 2 1 Answer: -Because the atomic number is 1, the amount of protons must be 1 as well -The mass number is equal to the amount of protons + neutrons, so, 1 + 2 = 3, therefore the mass number is 3 -Because there are more neutrons than protons, the atom IS an isotope -Because we have no electrons and 1 proton, this give the atom a +1 charge -Since we know the mass number and atomic number, we can write the symbol (this particular isotope of hydrogen is called tritium and is highly radioactive)
Summarize:(you can always write you own) • What is an atom made up of? Where is the mass of an atom located? What part of the atom is made up of “empty space” • Explain why it is more convenient to work with AMU’s (Atomic Mass Unit’s) versus grams: (In other words, which number would you rather work with, 1 AMU or 1.66 x 10-24grams?) • Compare and contrast the atomic number with the mass number, what's the difference? • What are isotopes? How do isotopes affect the mass number of an atom? • How do atoms become cationsand anions?
