IOns Charged Atoms

Why would an atom lose or gain electrons??? Neutral atoms ‘want’ their electrons to be in a stable configuration Usually means that the outermost shell is full of e’s The Nobel Gases (last column on the right) naturally have a full outer shell and are therefore stable Elements try to get the same number of electrons as the closest Nobel Gas Gain to look like the NEXT one Lose to look like the PREVIOUS one Depends on the which option needs the least amount of energy (ionization energy)

When an atom forms an ion The ion is physically different from the original atom Anions are larger than their parent atoms Cations are smaller than their parent atoms The ion is chemically different from the original atom Examples: Fluorine atom is the most reactive element (can even dissolve glass). Fluoride ion is much less reactive and essential to dental health. Cells require sodium and potassium ions for proper function. Sodium and potassium atoms are harmful to cells – react violently with water!

HOW does an atom carry a negative charge? To form a negatively charged ion An atom would need to GAIN electrons to fill its outer shell (and LOOK stable – like a noble gas) Called an ANION For example: Chloride ion Formed when the Chlorine atom(17 p’s & 17 e’s) GAINS an additional electron (17 p’s &18 e’s)  17 + 17 - e- + 18 - NOTE: the # of protons DIDN’T change!

HOW does an atom carry a negative charge? Notice: ANIONS have a different name then their parent atom The ending is removed and –ide is added Fluorine  Oxygen  You MUST know Non-metals tend to form anions oxygen family will form anions with a 2- charge (O2-, S2-, etc.) halogen family will form anions with a 1- charge (F-, I-, etc.) the superscript tells you the charge of the ion Fluoride Oxide

Learning Check 2- Oxygen family 1- 3 electrons Sulfide If an atom with 16 protons GAINS 2 electrons, what will it’s new charge be? What family does this atom belong to? What charge will any member of the halogen family carry? How many e’s does an atom with a 3- charge gain? What is the name of the ion formed from sulfur? How does it form? 2- Oxygen family 1- 3 electrons Sulfide By GAINING 2 electrons

HOW does an atom carry a positive charge? To form a positively charged ion An atom would need to LOSE electrons, losing its outer shell (the atom’s inner shell is full so it will LOOK stable) Called an CATION For example: Magnesium ion Formed when the Magnesium atom (12 p’s & 12 e’s) loses 2 electrons (12 p’s &10 e’s) 12 + 12 -  10 - + 2 e‑ NOTE: the # of protons DIDN’T change!

HOW does an atom carry a positive charge? Notice: CATIONS have the same name as their parent atoms You MUST know Metals tend to form cations alkali metals will form cations with a 1+ charge (Li+, Rb+, etc.) alkaline earth metals will form cations with a 2+ charge (Be2+, Ca2+, etc.) the superscript tells you the charge of the ion Transition metals can form different cations For example, Iron can form Fe2+ or Fe3+ - depends on what it is doing with its electrons to look stable

Learning Check 1+ Alkali metals 2+ 3 electrons Calcium If an atom with 19 protons LOSES 1 electron, what will it’s new charge be? What family does this atom belong to? What charge will any member of the alkaline earth metals family carry? How many e’s does an atom with a 3+ charge lose? What is the name of the ion formed from calcium atom? How does it form? 1+ Alkali metals 2+ 3 electrons Calcium By LOSING 2 electrons

Very Special Ions POLYATOMIC IONS First Quiz – Mon/Tues Sept 19/20! There is a very special group of ions known as POLYATOMIC IONS charged entities composed of several atoms bound together that stay together when forming larger compounds You MUST know 22 of the most common polyatomic ions (their formula, including charge & name) and be able to recognize them in formulas! First Quiz – Mon/Tues Sept 19/20!

Formula Name C2H3O2- Acetate HPO42- ClO- Hypochlorite HSO4- Hydrogen phosphate ClO- Hypochlorite HSO4- Hydrogen sulfate ClO2- Chlorite MnO4- Permanganate ClO3- Chlorate NH4+ Ammonium ClO4- Perchlorate NO2- Nitrite CN- Cyanide NO3- Nitrate CO32- Carbonate O22- Peroxide Cr2O72- Dichromate OH- Hydroxide CrO42- Chromate PO43- Phosphate H2PO4- Dihydrogen phosphate SO32- Sulfite HCO3- Hydrogen carbonate SO42- Sulfate