Nā nīnau hoʻohālike e kūkākūkā ana i nā pilina Covalent
Pendahuluan
ʻO kahi pilina covalent kahi ʻano pilina kemika kahi e kaʻana like ai nā ʻātoma ʻelua i kahi pālua a ʻoi aku paha mau electrons e hoʻokō ai i kahi hoʻonohonoho electron paʻa, e like me nā kinoea hanohano. ʻO kēia pilina maʻamau e hana ma waena o nā ʻātoma non-metal i loaʻa nā electronegativities kiʻekiʻe a ʻaʻole ʻokoʻa nui. He kuleana koʻikoʻi ka hoʻokumu ʻana o ka pilina covalent i ka kemika organik a me ka inorganic a ʻo ia ke kumu o nā hui he nui a mākou e hālāwai ai i kēlā me kēia lā. Ma kēia ʻatikala, e kūkākūkā mākou i kekahi mau laʻana e pili ana i nā pilina covalent a hāʻawi i nā hoʻonā e kōkua iā mākou e hoʻomaopopo maikaʻi iā lākou.
Nā Nīnau Laʻana a me ke Kūkākūkā
Nīnau 1
E hoʻoholo i ke ʻano a me ka helu o nā pilina covalent i hoʻokumu ʻia i loko o ka molekole H2O (wai).
Kūkākūkā:
Aia i loko o kahi molekole wai hoʻokahi ʻātoma oxygen (O) a me ʻelua mau ʻātoma hydrogen (H).
1. Hoʻonohonoho ʻana o ka Electron:
– Oxygen: 1s² 2s² 2p⁴ (ka huina o 8 mau electrons)
– Hydrogen: 1s¹ (huina 1 electron)
Pono ka oxygen i ʻelua mau electrons hou aʻe e hoʻokō ai i kahi hoʻonohonoho octet (8 mau electrons i loko o kona pūpū waho loa), ʻoiai ʻo kēlā me kēia ʻātoma hydrogen e pono ai i hoʻokahi electron e hoʻokō ai i kahi hoʻonohonoho duplet (2 mau electrons i loko o ka pūpū K).
2. Ka Hoʻokumu ʻana o nā Pilina Covalent:
– Kaʻana like kēlā me kēia ʻātoma Hydrogen i hoʻokahi electron me kahi ʻātoma Oxygen.
– Kaʻana like ka Oxygen i ʻelua mau electrons me ʻelua mau ʻātoma Hydrogen, hoʻokahi no kēlā me kēia ʻātoma.
No laila, ua hoʻokumu ʻia ʻelua mau pilina covalent i loko o ka molekole H2O, hoʻokahi ma waena o ka ʻātoma Oxygen a me ka ʻātoma Hydrogen.
Nīnau 2
E kākau i ke ʻano Lewis no ka molekole methane (CH₄).
Kūkākūkā:
ʻO ka methane he ʻātoma kalapona hoʻokahi (C) a me ʻehā mau ʻātoma hydrogen (H).
1. Hoʻonohonoho ʻana o ka Electron:
– Kalapona: 1s² 2s² 2p² (ʻeono mau electrons i ka huina)
– Hydrogen: 1s¹ (huina 1 electron)
ʻEhā mau electrons valence (2s² 2p²) ko ke kalapona, a pono i ʻehā mau electrons hou aʻe e hiki ai i kahi octet.
2. Ka Hoʻokumu ʻana o nā Pilina Covalent:
– Kaʻana like kēlā me kēia ʻātoma Hydrogen i hoʻokahi electron me kahi ʻātoma Carbon.
– Kaʻana like ke kalapona i ʻehā mau electrons me ʻehā mau ʻātoma Hydrogen, hoʻokahi no kēlā me kēia ʻātoma.
ʻO ke ʻano Lewis no ka methane penei:
".
H
|
H – C – H
|
H
".
Aia ke kalapona ma ke kikowaena me ʻehā mau pilina covalent hoʻokahi i ʻehā mau ʻātoma hydrogen.
Nīnau 3
E hoʻoholo i ka ʻano Lewis a me ke ʻano molekala no ke kalapona ʻokikene (CO₂).
Kūkākūkā:
Aia ke kalapona ʻokikene i hoʻokahi ʻātoma kalapona (C) a me ʻelua mau ʻātoma oxygen (O).
1. Hoʻonohonoho ʻana o ka Electron:
– Kalapona: 1s² 2s² 2p² (ʻeono mau electrons i ka huina)
– Oxygen: 1s² 2s² 2p⁴ (ka huina o 8 mau electrons)
ʻEhā mau electrons valence ko ke kalapona, ʻoiai ʻeono ko kēlā me kēia ʻātoma oxygen. Pono ke kalapona i ʻehā mau electrons hou aʻe no kahi octet, ʻoiai ʻelua hou aʻe ko kēlā me kēia ʻātoma oxygen.
2. Ka Hoʻokumu ʻana o nā Pilina Covalent:
– Kaʻana like ke kalapona i ʻelua mau electrons me kēlā me kēia ʻātoma Oxygen.
– Hoʻokumu ʻia ʻelua mau pilina covalent pālua ma waena o ke kalapona a me kēlā me kēia Oxygen.
ʻO ke ʻano Lewis no CO₂ penei:
".
ʻO = C = ʻO
".
He laina ke ʻano o ka molekala me kahi kihi hoʻopaʻa o 180°.
Nīnau 4
E helu i ka huina o nā electrons valence a kahakiʻi i kahi ʻano Lewis no ka mole ammonia (NH₃).
Kūkākūkā:
ʻO ka ʻamonia he ʻātoma naikokene hoʻokahi (N) a me ʻekolu mau ʻātoma hydrogen (H).
1. Hoʻonohonoho ʻana o ka Electron:
– Naikokene: 1s² 2s² 2p³ (7 mau electrons a pau)
– Hydrogen: 1s¹ (huina 1 electron)
ʻElima mau electrons valence ko ka naikokene, e pono ai ʻekolu mau electrons hou aʻe no kahi octet.
2. Ka huina o nā electrons Valence:
– Naikokene: 5 mau electrons valence.
– Hydrogen (3 mau ʻātoma): 3 mau electrons (1 electron no kēlā me kēia ʻātoma).
ʻO ka huina o nā electrons valence = 5 + 3 = 8 mau electrons valence.
3. Ka Hoʻokumu ʻana o nā Pilina Covalent:
– Kaʻana like ka naikokene i hoʻokahi uila me kēlā me kēia ʻātoma Hydrogen.
ʻO ke ʻano Lewis no NH₃ penei:
".
H
|
H – N – H
|
".
A aia kahi pālua o nā electrons manuahi (lone pair) i loko o ka naikokene.
Nīnau 5
E kaha kiʻi a wehewehe i ke ʻano Lewis no ka ion nitrate (NO₃⁻).
Kūkākūkā:
He hui polyatomic ka ion nitrate me hoʻokahi nitrogen (N) a me ʻekolu oxygen (O), a me kahi hoʻopiʻi maikaʻi ʻole.
1. Hoʻonohonoho ʻana o ka Electron:
– Naikokene: 1s² 2s² 2p³ (7 mau electrons a pau)
– Oxygen: 1s² 2s² 2p⁴ (ka huina o 8 mau electrons)
ʻElima mau electrons valence ko ka naikokene, ʻoiai ʻeono mau electrons valence ko kēlā me kēia oxygen.
2. Ka huina o nā electrons Valence:
– Naikokene: 5 mau uila.
– ʻOkikene (3 mau ʻātoma): 18 mau electrons (6 mau electrons no kēlā me kēia ʻātoma).
– Keu ma muli o nā iona maikaʻi ʻole: 1 uila.
ʻO ka huina o nā electrons valence = 5 + 18 + 1 = 24 mau electrons valence.
3. Ka hoʻokumu ʻana o nā pilina Covalent a me ka hoʻomākaukau ʻana o nā ʻano Lewis:
– Hoʻokumu ka naikokene i kahi pilina pālua me kekahi o nā ʻātoma oxygen a me nā pilina hoʻokahi me nā ʻātoma oxygen ʻelua ʻē aʻe.
– ʻO ka hoʻokaʻawale like ʻana o ka hoʻouku maikaʻi ʻole ma waena o ʻelua mau ʻātoma oxygen me nā pilina hoʻokahi e pili ana i ka resonance.
ʻO ke ʻano Lewis no NO₃⁻ penei:
".
O
/
ON = O
".
Akā, pono e hoʻohui ʻia kahi hōʻailona resonance e wehewehe i ka electron delocalization.
Ka hopena
ʻO ka hoʻopaʻa ʻana o Covalent kahi manaʻo nui i ka kemika, kahi e kaʻana like ai nā ʻātoma i nā electrons e hoʻokō ai i ke kūpaʻa. ʻO ka hoʻomaopopo ʻana i ke kaha kiʻi ʻana i nā ʻano Lewis, ka helu ʻana i nā electrons valence, a me ka hoʻoholo ʻana i nā ʻano molekala he mau mākau koʻikoʻi no ka hoʻomaopopo hohonu ʻana i nā kaʻina hana kemika. Ma o nā laʻana ma luna, ua manaʻolana ʻia e loaʻa i ka poʻe heluhelu kahi ʻike maikaʻi aʻe i ka hoʻokumu ʻia ʻana a me nā ʻano o nā pilina covalent.
